The JI
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     
 

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hong, K.
Right arrow Articles by Ehrhardt, R. O.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hong, K.
Right arrow Articles by Ehrhardt, R. O.
Right arrowPubmed/NCBI databases
*Gene*GEO Profiles
*HomoloGene*UniGene
*Compound via MeSH
*Substance via MeSH
Medline Plus Health Information
*Psoriasis
The Journal of Immunology, 1999, 162: 7480-7491.
Copyright © 1999 by The American Association of Immunologists

IL-12, Independently of IFN-{gamma}, Plays a Crucial Role in the Pathogenesis of a Murine Psoriasis-Like Skin Disorder

Kenneth Hong1,*, Alvina Chu1,*, Björn R. Lúdvíksson{dagger}, Ellen L. Berg* and Rolf O. Ehrhardt2,*

* Protein Design Labs, Inc., Fremont, CA 94555; and {dagger} Mucosal Immunity Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
The onset of acute psoriasis and the exacerbation of chronic psoriasis are often associated with a history of bacterial infection. We demonstrate that while only few scid/scid mice develop disease when CD4+CD45Rbhigh T cells are transferred alone, coadministration of LPS plus IL-12 or staphylococcal enterotoxin B into scid/scid mice 1 day after CD4+CD45Rbhigh T cell transfer greatly enhances disease penetrance and severity. Most importantly, the skin lesions induced by this method exhibit many of the histologic hallmarks observed in human psoriasis. Skin infiltrating CD4+ T cells were predominantly memory/effector cells (CD45Rblow) and exhibited a highly polarized Th1 phenotype. To test whether the development of pathogenic T cells was dependent on their production of IFN-{gamma}, we transferred IFN-{gamma}-/- CD4+CD45Rbhigh T cells into scid/scid or into T, B and NK cell-deficient scid/beige mice. Surprisingly, the incidence of psoriasis was similar to scid/scid animals that received IFN-{gamma}+/+ T cells, although acanthosis of the skin was attenuated. In contrast, the development of psoriasis was abolished if anti-IL-12 mAb was administered on day 7 and 35 after T cell transfer. Skin-derived IFN-{gamma}-/- inflammatory cells, but not cells from anti-IL-12-treated animals, secreted substantial amounts of TNF-{alpha}, suggesting that the inflammatory effect of IFN-{gamma}-/- T cells may be partly exerted by TNF-{alpha} and that the therapeutic effect of anti-IL-12 may depend on its ability to down-regulate both TNF-{alpha} and IFN-{gamma}. Overall, these results suggest that IL-12, independently of IFN-{gamma}, is able to induce pathogenic, inflammatory T cells that are able to induce psoriasiform lesions in mice.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Psoriasis is a chronic inflammatory skin disease that is associated with hyperplastic epidermal keratinocytes and infiltrating mononuclear cells, including CD4+ memory T cells, neutrophils, and macrophages (reviewed in Refs. 1–3). Because of this highly mixed inflammatory picture and the resulting complex interrelationships between these different cells, it has been very difficult to dissect the mechanisms that underlie the induction and progression of the disease. Indeed, whether genetically determined alterations in keratinocyte proliferation or immunoregulatory defects are the primary cause of psoriasis is currently unresolved. Some investigators believe that environmental factors, such as microbial infection and trauma, can be an initiating event in the pathogenesis of the disease (4, 5, 6, 7). This hypothesis also implies that although dormant autoreactive T cells may pre-exist in susceptible individuals, an environmental stimulus is necessary to trigger disease induction. Others believe that the immune system plays only a minor modulatory role in the disease process and that hyperproliferation of keratinocytes is in fact the initiating event in a genetically susceptible host.

Research into the pathogenesis of psoriasis has long been hindered by the lack of suitable animal models. Although several rodent models of skin inflammation have been recently introduced, in none of these models have specific T cell abnormalities been demonstrated as a primary cause for the induction of disease (8, 9, 10, 11, 12, 13, 14). Most recently, Schon et al. (15) presented evidence that a particular splenic T cell subset (CD4+CD45Rbhigh), the same T cell subset that induces colitis in scid/scid mice, is able to induce psoriasis-like lesions when transferred into a minor haplotype mismatched scid/scid mice. Other investigators have demonstrated that when pre-psoriatic skin, but not skin from healthy donors, is engrafted onto scid/scid mice, the transplanted skin develops into psoriasiform lesions after autologous blood-derived immunocytes are activated by staphylococcal enterotoxin B (SEB)3 and IL-2 and injected into the dermis (16, 17). In addition, patients that received fragments of diphtheria toxin linked to human IL-2 (DAB389IL-2), which selectively targets activated T cells but not keratinocytes, showed significant clinical improvement, indicating that T cells and not keratinocytes are the primary pathogenic component in the disease (18). Although these observations provide enough first evidence to support the concept that psoriasis-like conditions can indeed result from unregulated T cell responses, they provide very little evidence on the specific mechanism and the cytokines that are involved in the induction of psoriasiform lesions.

Bacteria and their products have been implicated as an initiating event in various T cell mediated autoimmune conditions in humans, including rheumatoid arthritis (RA) and inflammatory bowel disease (IBD) (6, 19). For example, in murine models of RA and IBD, mice do not develop inflammatory lesions under germfree conditions (20, 21, 22, 23, 24, 25). Indeed, either normal luminal bacteria (26) or infection with a single microbial pathogen have been shown to significantly increase the expression of disease (27, 28). LPS and SEB are important bacterial-derived immunomodulators, since they are not only able to activate immune-competent cells but are also able to increase the expression of cell adhesion molecules on vascular endothelial cells and T cells and thereby promote the entry of inflammatory cells into tissues (29, 30, 31, 32, 33, 34, 35). IL-12 produced very early during infection in vivo has important proinflammatory functions. It plays a key role in the differentiation of naive T cells into IFN-{gamma}-producing Th1 cells (36) and thus seems to be important in the induction of many T cell-mediated autoimmune diseases (21, 37, 38, 39, 40, 41, 42).

The role of IFN-{gamma} in autoimmunity has been more controversial. Although IFN-{gamma} production seems to be a hallmark of inflammatory T cells involved in numerous autoimmune conditions, it is less clear what function IFN-{gamma} actually plays in the disease process. Studies in animal models of inflammation and autoimmunity and in humans revealed that IFN-{gamma} can have opposing immunosuppressive or immunostimulatory effects depending on the disease and the time of application (reviewed in 43). In psoriasis, IFN-{gamma} is thought to play an important primary role in the disease pathogenesis, since T cells isolated from psoriatic lesions of patients secrete high amounts of IFN-{gamma} (44, 45) and T cell clones obtained from psoriatic skin directly promote keratinocyte proliferation through an IFN-{gamma}-dependent pathway (46).

In this study, we further dissect the pathogenic mechanism of psoriatic lesions by asking what role IL-12 and IFN-{gamma} play in the induction of pathogenic T cells in psoriasis. In particular, we ask whether IL-12, which in itself is an important up-regulator of IFN-{gamma} production, is able to induce chronic psoriasiform skin inflammation in the absence of IFN-{gamma}. We demonstrate that the injection of bacterial products and IL-12 significantly enhances penetrance and severity of psoriasiform lesions in this newly described murine model of psoriasis. Furthermore, we demonstrate that the pathogenesis of disease is driven by an IL-12-dependent, but IFN-{gamma}-independent mechanism, suggesting a novel strategy for therapeutic intervention in patients with psoriasis.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Mice

Female BALB/c mice and BALB/c-IFN-{gamma}-/- mice (donor mice) were purchased from The Jackson Laboratory (Bar Harbor, ME). C.B-17/Icr scid/scid mice and C.B-17 scid/beige double mutant mice (recipient mice) were purchased from Taconic Farms (Germantown, NY). All mice were housed in a specific pathogen-free environment at the Protein Design Labs animal facility and were used between 4 and 12 wk of age. Sentinel mice were used to screen for the following pathogens: Mouse hepatitis virus (MHV), Sendai virus, Pneumonia virus of mice (PVM), Reovirus serotype 3 (REO3), Theiler’s murine encephalomyelitis virus (TMEV), Myco-plasma. pulmonis, and parvovirus. Random screens of mice for pinworms were also conducted. None of the pathogens listed above were detected at any time. Mice were housed 2–5/microisolator. All scid/scid or scid/beige mice were handled with gloves under a class II hood, fed sterile food and water ad libitum, and maintained inside a laminar flow tent (Bioclean, Maywood, NJ) in sterile microisolators that were changed weekly. Donor mice were housed in conventional cages that were changed weekly.

Cell purification, and injection into scid/scid mice

Spleens were collected from 6- to 12-wk-old donor mice (BALB/c or IFN-{gamma}-/--BALB/c) and splenocytes were isolated by mechanical homogenization of whole spleens. CD4+ T cells were selected by positive selection. In brief, a cell suspension of pooled splenocytes from four to five donor mice was incubated with anti-CD4 (L3T4) Ab coated magnetic beads (Dynabeads, catalog no. 114.05, Dynal, Lake Success, NY) for 20–30 min at 4°C and separated by magnetic cell sorting with a Dynal Magnetic Particle Concentrator (MPC). Cells were removed from the cell-bead complex with Dynal DETACHaBEAD, and isolated from beads using a Dynal MPC. The resulting CD4+ enriched population was >90% pure. The cell suspension (10 x 106 cells/ml) was then incubated with Fc block (anti-CD32, 01241A; PharMingen, San Diego, CA) (10 µg/ml) and labeled with anti-CD4-FITC (9004D; PharMingen) and anti-CD45RB-PE (01145A; PharMingen) (both at 10 µg/ml) for 30 min at 4°C, washed, and sorted using a FACStar (Becton Dickinson, San Jose, CA) cell sorter. Double positive cells (CD4+CD45Rb+) were collected, selecting the cells that expressed high levels of CD45Rb (brightest 45%). The collected cell population was >90% pure and viable. Cells were then washed in cold PBS (D8662; Sigma, St. Louis, MO) and resuspended in PBS at 1.5 x 106 cells/ml. C.B-17/Icr scid/scid mice, aged 4–6 wk, were injected i.v. with 3 x 105 cells each, 200 µl total volume into the tail vein.

Induction and treatment of psoriasiform lesions in scid mice

To study the effect of microbial products and IL-12, recipient mice were treated as follows. A control group received CD4+CD45Rbhigh sorted cells with no additional treatment. A second group was given 20 µg LPS from Salmonella enteritidis (Sigma; L-2012) s.c. or i.p. per mouse on day 1 after cell transfer. A third group received 10 ng IL-12 (PharMingen) alone per mouse delivered s.c. or i.p. on days 1 and 3. The final group was injected s.c. or i.p. with a combination of LPS and IL-12. Dosage studies were conducted using 2, 10, and 100 ng doses of IL-12 in conjunction with 20 µg LPS. The LPS and IL-12 injection was given on day 1 following T cell transfer and an additional dose of IL-12 was administered on day 3. In additional studies, LPS (20 µg) and IL-12 (10 ng) were administered once weekly for 3 wk. Some experimental groups received 10 µg SEB protein from Staphylococcus aureus (Sigma S4881) i.p. per mouse once on day 1 following T cell transfer.

To study the role of IFN-{gamma}, T cells from BALB/c-IFN-{gamma}-/- mice (The Jackson Laboratory) T cells were isolated by the same methods described above. Recipient scid/scid mice were also coinjected with 20 µg LPS and 10 ng IL-12 on day 1 and 10 ng of IL-12 on day 3. In addition, scid/beige mice (Taconic Farms), that are T, B, and NK cell deficient, were used as recipient mice for IFN-{gamma}-/- T cell transfer in some experiments. For interventional studies, 0.5 mg anti-IL-12 (clone C17.8; PharMingen) was given i.p. to mice on day 7 and 35. Control mice received either PBS or rat IgG (Sigma) on the same day.

Clinical evaluation

Mice were evaluated by three different investigators at weekly intervals commencing on week 4 and ending on week 10. To record disease progression semiquantitative clinical scores from 0 to 4 were given based on physical appearance and ear thickness: 0 = no skin or ear symptoms; 1 = mild, moderate erythema on ears or eyelids with mild thickening of the ear (<2% of the body surface); 2 = moderate to severe erythema on one location (mostly ear and face) (2–10% of the body surface), mild scaling; 3 = severe erythema at two or more sites (ear, face, trunk) (>10% of the body surface), severe scaling; 4 = very severe, extensive erythema throughout the body (>20% of the body surface) with severe scaling. Specific observations were noted based on fur condition, ear manifestations, eyelid appearance, and presence of inflammation on limbs and tail. Ear thickness was determined using a modified spring micrometer (Oditest; Dyer, Lancaster, PA). Measurements were taken from the same part of the ear for all data time points from both the right and left ear. The micrometer was allowed to settle while on the ear to prevent tissue edema from affecting final measurement.

Histopathologic analysis

Necropsies were performed on mice at week 10–12 after cell transfer. Tissue samples from ear, eyelid, and tail were collected and fixed in paraformaldehyde solution and submitted to Comparative Bioscience (Sunnyvale, CA) for section preparation and analysis. To record disease severity, semiquantitive histological scores from 0 to 4 were given based on the severity of inflammation. Initial histological evaluation was performed in a blinded fashion by an independent outside pathologist. In later studies evaluation was blindly conducted by three different investigators. Mice which had ear thickness of 25 µm or less with no additional clinical signs were automatically given a histology score of zero without section analysis: 0 = no signs of inflammation; 1 = very low focal areas of infiltration, mild acanthosis; 2 = low level of mononuclear cell infiltration, mild thickening of epidermis, mild to moderate acanthosis; 3 = high level of mononuclear cell infiltration, high vascular density, thickening of the epidermis (acanthosis, rete pegs and hyperplasia of epidermis and keratinocytes, microabscesses, thinning of the granular cell layer); 4 = very extensive infiltration in epidermis and dermis, very high vascular density, extreme thickening of epidermis, pustule formation and destruction of granular cell layers.

Tissue samples were collected and embedded in Tissue Tek OCT (Miles, Elkhurt, IN) compound and frozen with dry ice for cryostat-cut sections. Tissue sections (5 µm) were fixed in 100% acetone and stained with PE-conjugated IL-12 mAb (p40/70) (PharMingen, clone C17.8). Tissues were evaluated as positive or negative based on visual fluorescent microscopy detection.

Skin infiltrating lymphocyte cell isolation

Skin infiltrating lymphocytes were isolated via enzyme digestion. In short, skin, ears, and eyelids were minced with sterile scissors, and the pieces were washed with HBSS over a 100-mm nylon cell strainer (Falcon, Becton Dickinson, Franklin Lake, NJ) to remove surface debris. Infiltrating cells were liberated by incubating the cut pieces in 25 ml of warm (37°C) HBSS media without Ca2+/Mg2+ (10-543F; BioWhittaker, Walkersville, MD) supplemented with 25 mM HEPES buffer (17-737E; BioWhittaker) and 10% FBS (HyClone, Logan, UT SH30071.03) for 20 min at 37°C. The remaining pieces were washed over nylon mesh, resuspended in RPMI 1640 medium (12-702F; BioWhittaker) augmented with 25 mM HEPES buffer, 10% FBS, 400 U/ml DNase (104159; Boehringer Mannheim, Indianapolis, IN), 400 U/ml collagenase (1088874; Boehringer Mannheim), and incubated 90 min at 37°C on a rocker. The resulting cell suspension was filtered sequentially through a 100-µm and 40-µm nylon mesh filter and then washed twice in RPMI 1640 medium supplemented with 25 mM HEPES and 10% FBS.

In vitro stimulation of skin infiltrating lymphocytes (SIL) and detection of cytokines

SIL were resuspended at 106/ml in complete RPMI 1640 medium supplemented with 10% FBS (HyClone), 5 x 10-5 M 2-ME (Sigma), 2 mM glutamine (Life Technologies, Gaithersburg, MD), 10 U/ml penicillin, 100 µg streptomycin (Life Technologies), and 15 mM HEPES. CD4+ sorted T cells were resuspended at 2.5 x 105/ml. A total of 200 µg/well of this suspension was then placed in a 96-well tissue culture plate to (3072 Falcon) and incubated for 48 h with anti-CD3 (clone 145-2C11; Protein Design Labs) and anti-CD28 (PharMingen), each at 1 µg/ml. Supernatants from three different culture wells were collected and tested by ELISA for IFN-{gamma}, TNF-{alpha}, and IL-4. The ELISA procedure involved coating a 96-well flat-bottom Immulon 4 plate (011-010-3850; Dynatech, Chantilly, VA) overnight at 4°C with 50 µl of a 2 µg/ml solution of anti-IFN-{gamma}, anti-TNF-{alpha}, or anti-IL-4 Ab (all from PharMingen) in carbonate buffer. Plates were then washed with PBS/Tween (0.05% Tween-20 in PBS) and blocked with 200 µl sterile solution of PBS with 3% BSA to (A7030 Sigma Bovine Albumin) for 1 h at 37°C. In between all of the following steps, plates were washed with PBS/Tween. IFN-{gamma}, IL-4, and TNF-{alpha} standards as well as sample supernatants were then added to wells and incubated for 2 h at 37°C. Biotin-conjugated secondary Abs for anti-IFN-{gamma}, anti-TNF-{alpha}, and anti-IL-4 (all Abs from PharMingen) were then added to the respective plates at 2 µg/ml in 3% BSA/PBS solution and incubated for 1 h at 37°C. HRP-labeled streptavidin (016-030-084; Jackson ImmunoResearch, West Grove, PA) was then added at a concentration of 1 µg/ml. O-Phenylenediamine to (4664 Sigma) was then used as substrate buffer per manufacturer’s protocol. Assay was then read on a Molecular Devices (Sunnyvale, CA) plate reader and data were analyzed using SOFTmax software.

Statistical analysis

Descriptive statistics and testing for significance of differences between treatment groups were assessed either by the two-tailed Student’s t test or by using the {chi}2 test using the Microsoft Excel (Redmond, WA) statistical program.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Treatment of scid/scid mice restored with CD4+CD45Rbhigh T cells with LPS plus low and medium doses of IL-12 results in increased incidence and severity of psoriasis: high doses of IL-12 prevent disease induction

Previous studies have demonstrated that scid/scid mice reconstituted with minor haplotype mismatched CD4+CD45Rbhigh BALB/c T cells sometimes develop chronic skin inflammation that resembles human psoriasis (15). In initial experiments, we found that when BALB/c CD4+CD45Rbhigh T cells alone were transferred to C.B-17 scid/scid mice, only a few animals exhibited psoriasiform lesions and the expression of disease was rather mild. This finding was consistent with previous observations made by Schon et al. (15). Because bacterial mitogens or bacterial superantigens have been shown to be potent modulators of cell-mediated immune responses, and IL-12 has been demonstrated to play an important role in the induction of various autoimmune conditions (reviewed in Refs. 36, 42, and 47), we tested initially whether the coadministration of such agents would have an effect on the induction of psoriasis in the scid/scid transfer model. As shown in Table IGo, when C.B-17 scid/scid mice were reconstituted with BALB/c CD4+CD45Rbhigh T cells alone, only 38% of the mice developed psoriasiform skin lesions and only 27% of the mice developed severe forms of disease. When LPS was coadministered alone, we observed a slight, but insignificant, increase in disease incidence (50%), and moreover the severity of the lesions remained similar to lesions in mice that had received cells alone. Similarly, coadministration of a medium dose (10 ng/mouse) of IL-12 alone on day 1 and 3 following T cell transfer led to an apparent increase in disease incidence (67%) without affecting disease severity.


View this table:
[in this window]
[in a new window]
  		Table I. In vivo administration of IL-12 in combination with LPS after CD4+CD45Rbhigh T cell transfer leads to a significant increase in disease expression

 
In contrast, recipient mice that received either 1 or 10 ng IL-12 on day 1 and day 3 along with 20 µg of LPS on day 1 following T cell transfer showed an increase in disease severity and incidence. In particular, the administration of a medium doses of IL-12 (10 ng/mouse) along with LPS showed a 73% incidence of disease with an average histology score of 2.25 ± 1.1, which was significantly higher than when PBS was coadministered (p < 0.008). In addition, the percentage of animals with severe disease in the IL-12 medium dose group was also higher (42%) when compared with the IL-12 low dose group (36%) and significantly higher when compared with the PBS control (27%). Interestingly, coadministration of LPS (20 µg/mouse) and a high dose of IL-12 (100 ng/mouse) completely inhibited disease development (incidence 0%). When LPS and medium doses of IL-12 (10 ng) were coadministered once a week for 3 wk the incidence of disease was 80% (8/10) with an average clinical score of 2.5 ± 1 (Table IGo). This particular induction protocol was also associated with an accelerated onset of disease as the animals in this group came down with disease as soon as 4 wk after T cell transfer (average time of onset, 4.7 ± 1.0 wk). In contrast, animals that had received only one dose of LPS and IL-12 (10 ng) developed disease at an average of 6.2 ± 1.7 wk after T cell transfer, and animals that received T cells only developed signs of disease at an average of 7.3 ± 2.0 wk after T cell transfer.

Animals that had received unsorted CD4+ T cells (1 x 106/mouse) never came down with disease even if they were treated with three administrations of LPS (20 µg) and IL-12 (10 ng) (Table IGo), indicating that LPS and IL-12 administration can only act on naive T cells and the regulatory effects of CD45Rblow cells cannot be overcome by the administration of microbial factors and IL-12. To ensure the presence of sufficient numbers of effector T cells in the unsorted cell population, we transferred up to 5 x 106 unsorted CD4+ T cells plus LPS and IL-12 three times to naive scid/scid mice in a different set of experiments; however, this approach also failed to induce disease lesions (data not shown). Of note, mice that received no T cells or T cells alone were housed together with mice that received T cells plus LPS and IL-12, to ensure that other exogenous factors did not play a role in the induction of disease.

In a different set of experiments, we tested whether other microbial products such as SEB exert an influence on disease expression as well. As shown in Table IGo, SEB was also able to induce disease at a higher incidence and severity (average clinical score, 1.5 ± 0.9) than cells alone, thus demonstrating that the ability of bacterial constituents to modulate the expression of psoriasiform lesions is not unique to LPS.

In separate cell transfer studies, we found that scid/scid mice that received inflammatory cells isolated from the skin lesions of diseased mice (4 x 106 cells were administered/mouse) did not develop psoriasis unless LPS and IL-12 was coadministered (data not shown), indicating that the transfer of inflammatory psoriatic T cells alone is not sufficient to induce a chronic inflammatory response in the skin.

Psoriatic skin lesions of scid/scid mice treated with LPS and IL-12 closely resemble human pathology

Animals that received CD4+CD45Rbhigh cells in conjunction with LPS and IL-12 developed disease symptoms as soon as 4–8 wk after cell transfer (see Table IGo). Mice without clinical signs of disease at week 10 post T cell transfer remained disease free for an additional 4–6 wk of observation. Thus, mice were monitored beginning on week 4, and necropsies were performed on subject animals between weeks 10 and 12. Clinical signs of disease consistently included increased erythema of the ear and thickened skin on ears and eyelids. Some animals also showed signs of significant skin inflammation on the tail. In more severe cases, skin inflammation was observed throughout the body with increased scaling and hair loss (clinical score 4) (Fig. 1GoJ). Ear thickness typically varied from a baseline of 21 ± 1.1 µm in undiseased animals to a pathological range of 26–50 µm. Skin that became severely affected consistently became scaly, ulcerated, and typically showed plaque-type elevation (see also Fig. 1GoJ). Skin inflammation in psoriatic mice ranged from mild, around the base of the ears and around the eyelids (clinical score 1–2), to severe hair loss that extended to over 75% of their body (clinical score 3–4) (see Materials and Methods). Since ear thickness correlated very well with the severity of disease and clinical scores, we used the measurement of ear thickness as an indicator for overall skin inflammation in most experiments.



View larger version (82K):
[in this window]
[in a new window]
  		FIGURE 1. Histological analysis of psoriasiform lesions in CD45Rbhigh T cell reconstituted scid/scid mice and treated with LPS and IL-12. All cross-sections were taken at x100 magnification. Tissue from normal scid/scid mice. A–C, Ear, eyelid, and tail; magnification x100. Tissue from scid/scid mice that received CD4+CD45Rbhigh T cells in combination with LPS (20 µg) and IL-12 (10 ng). D, Ear; note the presence of the major hallmarks of psoriasis: acanthosis (i.e., thickening of the epidermis) and hyperkeratosis (i.e., thickening of the cornified layers) with some ulcer or erosion formation and epidermal (micro)-abscess formation, and mononuclear lymphocyte infiltration (magnification, x100). E, eyelid; the same hallmarks of psoriasis can also be seen here with the addition of elongated rete peg formations (i.e., down-growths of epidermis into dermis) (arrows) (magnification, x100). F, Tail; note elongated rete pegs (arrows) as well as severe acanthosis with aggregations of neutrophils forming abscesses. Vessels are surrounded by mononuclear cells contain large numbers of marginated neutrophils (magnification, x100). G, Tissue (ear) from scid/scid mice that received IFN-{gamma}-deficient CD4+CD45Rbhigh T cells and LPS plus IL-12 (10 ng). The acanthosis is less severe than in the scid/scid mice that received wild-type T cells (magnification, x100). H, Tissue (ear) from scid/beige mice that received IFN-{gamma}-deficient CD4+CD45Rbhigh T cells and LPS plus IL-12 (10 ng). The acanthosis, but not the inflammation, is less severe than in the scid/scid mice that received wild-type T cells (magnification, x100). I, Tissue (ear) from mice treated twice with anti-IL-12 (0.5 mg each time). The skin tissue is indistinguishable from sample shown in A (magnification, x100). J, scid/scid mouse with severe psoriasis after CD45Rbhigh T cell transfer and administration of LPS (20 µg) and IL-12 (10 ng). The mouse shows extensive hair loss, severe erythema with ulceration and scaling with plaque-like elevations, especially on ear and face (clinical score 4).

 
Other psoriasis-like models in mice have been criticized for not possessing the histological characteristics found in human forms of disease. Differences in the mouse skin structures were deemed responsible for these discrepancies. An absence of elongation of rete pegs (i.e., down-growths of epidermis into dermis) in mice, a major hallmark in human disease, was attributed to the relatively flat dermoepidermal junction in mice (8, 48). Histological analysis of the lesions induced by our protocol was performed by taking biopsies of skin samples from several areas of diseased mice and examining 3-µm sections stained with hematoxylin and eosin. Samples taken from the ear, eyelid, and tail of diseased mice that had received T cells plus LPS (20 µg/mouse) and IL-12 (10 ng/mouse) were prepared for histologic evaluation and microscopically examined by an independent pathologist. Most lesions were found to have typical signs of hyperkeratosis, including orthokeratosis (i.e., layers of anucleated cornified cells) and parakeratosis (i.e., layers of nucleated cornified cells) with some ulcer or erosion and pustule formation (Fig. 1Go, D and H). Also noted was a thickening of the epidermis (acanthosis) with proliferation of the keratinocytes and moderately deep rete pegs in the subcutis (Fig. 1Go, D and E); the inflammatory cell infiltration consisted of primarily mononuclear cells composed of lymphocytes with fewer monocytes, macrophages and plasma cells. Variable numbers of neutrophils with a few eosinophils were also seen. Capillaries and other vessels were numerous, contained large numbers of marginated neutrophils and were typically surrounded by lymphocytes (Fig. 1Go, D–H). The combination of these characteristics indicate that the psoriasiform lesions in this model are very comparable to those found in humans. Immunohistochemistry staining of the skin and FACS analysis of infiltrating lymphocytes revealed that beside numerous CD4+ T cells, no endogenous CD8+ T cells were present in the skin lesions (data not shown). Fig. 1Go, A–C, is representative of the histology found in skin from normal scid/scid mice that received no T cells. Sections from these mice were taken at the same age as diseased mice. The epidermis is 1–2 cells thick and the dermis contains almost no lymphocytes. In addition, the density of vessels is sparse. The junction of the dermis to the epidermis is straight and contains no abscesses.

Of note, as one might expect from this model, various degrees of inflammation were observed in the colon of these animals as well. Interestingly, the administration of LPS and IL-12 (medium) did not lead to an increase in severity of colitis, but rather to a decrease of inflammation in the colon (average histological score: PBS, 2.5; LPS + IL-12 (10 ng), 1.0). No other marked pathological changes were observed in other organs (liver, lung) besides an occasional splenomegaly with and without infiltration of CD4+ T cells (data not shown).

CD4+ T cells from the skin of mice with psoriasis are CD45Rblow and produce high levels of IFN-{gamma} and low levels of IL-4

To compare the activation/cytokine profile of SIL, we purified this population from the skin lesions of diseased and undiseased mice. Isolated SIL were stimulated in vitro with anti-CD3 and anti-CD28 for 48 h, and supernatants were tested for the production of IFN-{gamma}, TNF-{alpha}, and IL-4. Lymphocytes isolated from the skin of mice that received T cells but showed no clinical signs of disease did not secrete any detectable levels of IFN-{gamma} or IL-4. In contrast, cells from diseased mice expressed very high levels of IFN-{gamma} and TNF-{alpha} and low levels of IL-4 (Table IIGo). This pattern of cytokine expression was confirmed by intracellular cytokine staining (data not shown). Naive CD4+CD45Rbhigh donor cells from spleens of BALB/c were stimulated in a similar fashion and showed no detectable levels of any cytokine tested. Furthermore, the majority of CD4+ cells isolated from the inflamed tissue of diseased mice were CD45Rblow (Fig. 2Go). The data suggest that the majority of naive T cells transferred into scid/scid mice differentiate in the microenvironment of the skin into Th1-like memory/effector T cells.


View this table:
[in this window]
[in a new window]
  		Table II. CD4+ T cells isolated from psoriatic lesions of scid/scid mice produce high levels of interferon-{gamma} and low levels of IL-41

 


View larger version (20K):
[in this window]
[in a new window]
  		FIGURE 2. CD4+ T cells isolated from psoriatic lesions express low levels of CD45Rb. Total cells from psoriasiform lesions were stained with APC-conjugated anti-CD4 and PE-conjugated CD45Rb. The histogram shows CD45 positive staining of gated CD4+ cells. Donor cells (open histogram) are compared with cells that were isolated from psoriasiform lesions (filled histogram). Data are representative of at least four independent experiments.

 
IFN-{gamma}-deficient CD4+CD45Rbhigh T cells are able to induce psoriasiform lesions in scid mice.

To examine whether IFN-{gamma} has a primary role in the induction of psoriasiform lesions, we first transferred naive T cells from IFN-{gamma}-deficient (IFN-{gamma}-/-) mice into C.B-17 scid/scid mice. Interestingly, we found that despite the lack of IFN-{gamma}, CD4+CD45Rbhigh T cells from IFN-{gamma}-/- donors were able to induce psoriasiform lesions in scid/scid mice (Fig. 3Go). Disease induction occurred with similar frequency, but ear thickness in diseased IFN-{gamma}-/- T cell scid/scid mice was, on average, less than in control mice, and skin lesions on eyes and face were present but were less pronounced. The average clinical score of the diseased mice was 0.9 ± 1.0, and only one case of severe psoriasis (clinical score >= 3) was noted (see Table IVGo). In addition, disease onset was delayed (10–12 wk after cell transfer), when compared with control mice (average of 6–8 wk after cell transfer). Consistent with these observations, it appeared that in particular the hyperkeratosis in the skin of IFN-{gamma}-/- T cell scid/scid mice was less pronounced (Fig. 1GoG).



View larger version (22K):
[in this window]
[in a new window]
  		FIGURE 3. Administration of anti-IL-12, but not the transfer IFN-{gamma}-/- CD4+CD45Rbhigh T cells, inhibits the development of psoriatic skin lesions in scid/scid mice. C.B-17 scid/scid mice were reconstituted with 3 x 105 CD4+CD45Rbhigh cells from the spleen of BALB/c mice and injected with 20 µg LPS on day 1 and twice with 10 ng IL-12 on day 1 and 3. Control mice received rat IgG Ab (n = 5). The experimental group was treated with anti-IL-12 mAb (clone C17.8 rat IgG1, PharMingen) on day 7 and 35 (n = 5, p < 0.001). In the IFN-{gamma}-/- T cells transfer group either scid/scid (n = 5, p < 0.005) or scid/beige mice (n = 7, p < 0.013) received 3 x 105 CD4+CD45Rbhigh from spleens of IFN-{gamma}-deficient mice. Recipient mice were treated with LPS and IL-12 as described above. Ear thickness is measured in µm and is reported in weekly time intervals. Data represents the average ± SEM of four to five animals per group of one experiment. One additional experiment of the control, anti-IL-12 group, and the IFN-{gamma}-/- group gave similar results. Statistical analysis was performed using the two-tailed Student’s t test.

 

View this table:
[in this window]
[in a new window]
  		Table IV. Incidence and clinical score of CD4+CD45Rbhigh scid mice

 
The absence of donor-derived IFN-{gamma} production was verified by testing the supernatants of isolated lymphocytes from the skin of diseased CD4+CD45Rbhigh IFN-{gamma}-/- reconstituted scid/scid mice after 48 h of stimulation with anti-CD3 and anti-CD28. No detectable levels of IFN-{gamma} (<=30 pg) were found in any of the samples when tested by ELISA (Table IIIGo). The expression of TNF-{alpha} was also measured and found to be elevated but significantly less than the TNF-{alpha} levels observed in mice reconstituted with CD4+CD45Rbhigh T cells from wild-type animals (Table IIIGo).


View this table:
[in this window]
[in a new window]
  		Table III. Anti-IL-12 treatment reduces T cell inflammatory responses significantly, and IFN-{gamma}-/- SIL produce TNF-{alpha}1

 
To further rule out that minute levels of IFN-{gamma} secreted by host NK cells are sufficient to induce disease, we injected IFN-{gamma}-/- T cells into scid/beige mice. These mice carry in addition to the scid mutations, the beige mutation that causes a deficiency in NK cells in addition to the T and B cell deficiency already present in the scid mutation. As shown in Fig. 1GoH, scid/beige mice that received IFN-{gamma}-/- CD4+CD45Rbhigh T cells also developed a very significant increase in ear thickness; however, again, the onset of disease was significantly delayed (Fig. 3Go) and the incidence of disease was reduced (Table IVGo) when compared with mice that had received IFN-{gamma}+/+ CD4+CD45Rbhigh T cells. In addition, the severity of disease as measured by ear thickness (Fig. 3Go) and clinical score (Table IVGo) was attenuated. Interestingly, despite the presence of severe mononuclear cell infiltration, the acanthosis, consistent with above results, was less pronounced in these animals (Fig. 1GoH). These results indicate that IFN-{gamma} regulates either directly or indirectly keratinocyte proliferation, but not mononuclear cell infiltration/activation in psoriasis.

IL-12 is highly expressed in psoriasiform lesions and in vivo neutralization of IL-12 down-regulates TNF-{alpha} and IFN-{gamma} and inhibits disease development

We next focused on IL-12, since this proinflammatory cytokine plays a key role in the induction of IFN-{gamma}. We performed immunohistochemical studies to detect the presence of heterodimeric IL-12 in inflamed tissue. The illustrations presented are anti-IL-12-PE stained 5-µm cross-sections from samples of ears of diseased mice. As shown in Fig. 4GoA, there is a very significant amount of IL-12 (p35/p40 (p70)) heterodimer expressed in the tissue of diseased CD4+CD45Rbhigh-treated mice. In contrast, significant less staining could be observed in CD4+CD45Rbhigh-treated animals that were injected with anti-IL-12 mAb (0.5 mg/mouse) on day 7 and 35 (Fig. 4GoB).



View larger version (16K):
[in this window]
[in a new window]
  		FIGURE 4. Immunohistochemical identification of heterodimeric IL-12 in the skin of scid/scid mice with psoriasis. A, High staining intensity of IL-12 heterodimer is seen in the skin of mice that were treated with control Ab (rat IgG). B, Few cells stain for IL-12 heterodimer in the skin of scid/scid mice that were treated twice i.p. with 0.5 mg of anti-IL-12 mAb (clone C17.8 rat IgG1) on day 7 and 35. Samples were taken 10 wk after T cell transfer and LPS and IL-12 (10 ng) administration. Tissue was stained with anti-IL-12 PE conjugated mAb (clone C17.8 rat IgG1; PharMingen) and photographed at x200 magnification, using Kodak 400 film.

 
To further evaluate the role of IL-12 in the induction of psoriasiform lesions, we administered anti-IL-12 mAb (0.5 mg) at day 7 and 35 after T cell transfer to scid/scid mice that had received wild-type CD4+CD45Rbhigh T cells. Two doses of anti-IL-12 mAb were given to maintain a high enough Ab titer over the entire period of disease induction after the transfer of CD4+CD45Rbhigh T cells. In two independent experiments, mice (group of five) that were treated with anti-IL-12 mAb were completely protected from developing disease. Only 1 mouse out of 10 developed visible mild psoriasis in the form of slight hair loss and erythema around the eyelids (clinical score 1); however, this mouse and all other mice treated with anti-IL-12 mAb did not develop any increase in ear thickness (Fig. 3Go). In contrast, control mice that were treated with rat IgG control Abs or with PBS showed an incidence of 90% (9 of 10 mice developed disease) with an average clinical score of 2.4 ± 0.7 (Table IVGo). The higher incidence and severity of disease in this group was also associated with a significantly higher increase in ear thickness over time (Fig. 3Go).

The ears and skin of mice that received anti-IL-12 were examined for the cytokine production of infiltrating lymphocytes. While there were very few lymphocytes present in the skin of anti-IL-12 treated animals, these were isolated and tested for IFN-{gamma}, IL-4, and TNF-{alpha} production. Only low levels of IFN-{gamma}, IL-4, and TNF-{alpha} were detected in the supernatants of cells isolated from treated animals when compared with the cytokine production of supernatants obtained from control animals (Table IIIGo).

The results above are corroborated by the analysis of the histopathological sections obtained from animals that were treated with anti-IL-12 mAb. Mice that had been treated with with 0.5 mg of anti-IL-12 mAb on day 7 and 35 lacked any signs of significant inflammation, acanthosis or hyperkeratosis (Fig. 1GoI). Thus, anti-IL-12 administration seems to prevent the development of psoriasiform lesions by inhibiting keratinocyte hyperproliferation and mononuclear cell infiltration most likely by down-regulating both IFN-{gamma} and TNF-{alpha} production.


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Psoriasis is a papulosquamous skin disease associated with rapid epidermal proliferation and a chronic mixed mononuclear cell infiltrate, including macrophages, dendritic cells, and activated T cells. Although this histopathology together with reports that administration of Abs against CD4 or fragments of diphtheria toxin fused to IL-2 may be beneficial in patients with psoriasis (18, 49, 50, 51, 52) suggest an important role of T cells in the pathogenesis of this disease, the precise function of such inflammatory T cells is still unknown. Recently, Schon et al. (15) provided direct evidence that T cells may play a central role in the pathogenesis of the disease, by demonstrating that the transfer of minor-haplotype mismatched naive T cells into scid/scid mice was able to induce psoriasiform lesions in these mice. In these experiments, the expression and time to induction of disease was highly dependent on the specific minor histocompatibility Ags expressed by the donor cells. For instance, when BALB/c donor cells were used, the psoriasiform lesions induced in scid/scid mice were typically mild. However, when using different donor cells from F2 (BALB/c x 129/SvJ) resulting in a greater genetic difference between donor and recipient mice, the authors were able to demonstrate a significant increase in the severity of the lesions. Although these studies were the first to show that T cells transferred into a scid/scid mouse can be directly responsible for the induction of psoriasis, they reveal little about the role of exogenous stimuli and the pathogenic mechanisms of the T cell involvement in the disease process.

Thus, we first examined in the present study the question of how immunomodulatory stimuli, in this case microbial Ags and the proinflammatory lymphokine IL-12, effect the ability of T cells to induce psoriasis in this newly developed CD4+CD45Rbhigh T cells transfer model. We show that coadministration of LPS and IL-12 (1 and 10 ng) led to a more rapid onset and to an increased incidence of psoriasis in C.B-17 scid mice. In addition, the observed lesions in treated mice were also more severe. In additional experiments, we were able to demonstrate that coadministration of SEB also led to a significant increase in disease incidence and expression. These findings are very intriguing in light of reports that a significant number of patients report bacterial or viral infections before the appearance of psoriasiform lesions (reviewed in Refs. 53–55) and in light of recent animal model data that have suggested a role of bacterial superantigens in the pathogenesis of psoriasis (17, 56). Most notably, the skin lesions that developed by this method of induction were characteristic and remarkably similar to human psoriatic lesions, exhibiting most clinical and histological hallmarks. The scaling and thickening of skin evident macroscopically was due to marked hyper, parakeratosis, and acanthosis. It is further documented in the microscopic appearance of elongated rete pegs, ulcer, and pustule formation, and in the often severe epidermal hyperplasia. The inflammatory cell infiltration was primarily mononuclear and composed of lymphocytes with fewer monocytes, macrophages, and plasma cells. Moreover, the majority of CD4+ T cells isolated from psoriasiform lesions express low levels of CD45Rb, which is consistent with the fact that recent studies in humans found that T cells isolated psoriatic plaques exhibit a memory phenotype (57). The above described histological characteristics (elongated rete pegs, microabscesses, acanthosis, hyperplasia, and hyperkeratosis) clearly distinguish this model from classic cutaneous graft-versus-host disease (GVHD), despite the fact that by definition through the use of minor haplotype mismatched T cells transfer this model could be interpreted as a GVHD model. Moreover, in contrast to psoriatic lesions, the histology of GVHD skin samples exhibits degenerating or necrotic keratinocytes, apoptotic basal cells surrounded by lymphocyte and dense dermal fibrosis (58), clearly not observed in this model. In fact, this and the SCID-hu xenogeneic transplantation model (17) are the only murine models of psoriasis to our knowledge in which the skin histology shows elongated rete pegs formation. Beside the similarity to the human histology observed in this study, there are also some differences. Most notable is the absence of CD8+ T cells in this model which can be found in the epidermis of psoriatic plaques in humans (59, 60, 61). So far, however, a primary role for CD8+ T cells in the pathophysiology of psoriasis has not been identified and successful initial therapies targeting CD4+ T cells rather than CD8+ T cells point toward the CD4+ T cells as the primary culprit of the disease (49, 50, 51, 52). Furthermore, the amount of CD8+ T cells seems to also vary significantly in different stages and types of psoriasis (60, 62). Nevertheless, further experiments have to address the role of CD8+ T cells in the CD4+ T cell transfer model.

Several mechanisms could be responsible for the disease-promoting effects of LPS, IL-12, and SEB. First, these immunomodulators may assist in the proliferation and differentiation of naive Th0 cells to Th1 cells. This is quite plausible, since IL-12 alone without TNF-{alpha} or IL-1 fails to activate T cells (63, 64, 65) and microbial products; in particular, LPS can induce the production of these proinflammatory lymphokines by macrophages. In fact, recent studies have shown that microbial products, such as LPS, can directly stimulate TNF-{alpha}, IL-6, and to a lesser extent IL-12 production by murine skin-derived dendritic cells (66), and thus may be responsible for setting the proinflammatory condition for autoreactive T cells. Recent studies by Segal et al. (37) demonstrate that microbial products (LPS, Escherichia coli DNA, CpG oligonucleotides) can directly activate dormant myelin-basic protein-specific T cells into effector cells capable of inducing murine encephalitis, an effect that is dependent on IL-12. Thus, it is possible that CD45Rbhigh T cells after the transfer into SCID mice require additional IL-12 dependent signals to develop into autoimmune effector cells.

In addition to their immunostimulatory effects on macrophages and their effects on the development of Th1 effector cells, LPS, IL-12, and SEB may also modulate leukocyte trafficking in recipient mice to result in the cutaneous localization of Th1 effector cells. LPS promotes leukocyte recruitment by stimulating endothelial cell expression of E-selectin, ICAM-1, and VCAM-1 adhesion molecules both directly and through its ability to induce the production of IL-1, TNF-{alpha} and IFN-{gamma} (reviewed in Refs. 67 and 68). The proinflammatory effects of these cytokines on leukocyte adhesion and migration is also well-known (67, 68). Most interestingly, in humans IL-12 and bacterial superantigens, such as SEB, have been demonstrated to induce the expression of the cutaneous lymphocyte Ag (CLA) on activated T cells (69). CLA+ T cells are highly enriched in chronic inflammatory skin disorders and CLA appears to function as a homing receptor for the skin as it is a ligand for endothelial cell E-selectin (70, 71, 72). Additional experiments will address the relationship of these observations in humans to our studies in mice.

IFN-{gamma} and IL-12 are two very important immunoregulatory cytokines that have been shown to play an important role in the development of autoimmune disorders (43, 73). IL-12 primarily activates NK and T cells, whereas IFN-{gamma} primarily activates macrophages and induces the up-regulation of class II molecules on tissue cells. While the key function of IL-12 is the induction and maintenance of IFN-{gamma} production in T cells during an immune response and in various autoimmune conditions, the role of IFN-{gamma} during such processes, in particular whether IFN-{gamma} is necessary for the IL-12 mediated generation of autoreactive inflammatory Th1 cells, has been controversial (36). Considering the presence of IFN-{gamma} in psoriatic plaques in humans as well as in animal models and its putative involvement in the epithelial and keratinocyte abnormalities observed in patients (74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85) and our findings that IFN-{gamma} is produced at very high levels by inflammatory T cells isolated directly from the lesions of psoriatic mice, one might have expected IFN-{gamma} to be crucial for the induction of autoimmune effector cells in psoriasis. The data in this paper, however, indicate that IFN-{gamma} may only participate in the disease process by enhancing disease severity, most likely by promoting keratinocyte proliferation, but clearly not by inducing and maintaining pathogenic, inflammatory T cells in psoriatic skin. This finding is supported by the fact that the histology observed in lesions of mice that received IFN-{gamma}-/- donor T cells showed slightly lesser or equal signs of inflammation but hyperkeratosis or acanthosis was clearly diminished in scid/scid or scid/beige mice. Moreover, although clinical severity of disease, as measured by ear thickness and macroscopic observation, was attenuated when compared with control animals, the incidence of disease was very similar. This was also found to be true when IFN-{gamma}-/- T cells were transferred into T, B, and NK cell-deficient scid/beige mice.

These results indicate that IFN-{gamma} might not play a major role in the induction of chronic skin inflammation, but seems to be an important cofactor in the induction of aberrant keratinocyte proliferation. Such a notion is supported by the fact that the IFN-{gamma} receptor is present on keratinocytes (75) and by the work of Prinz et al. (46), in which they demonstrate that lesional psoriatic T lymphocytes are capable of promoting keratinocyte proliferation in vitro and that such mitogenic capacity can be inhibited by the addition of serum containing Abs against IFN-{gamma}. Others have shown that IFN-{gamma} is able to promote keratinocyte proliferation in the presence of psoriatic fibroblasts but not in the presence of healthy fibroblasts (83). In addition, it is possible that IFN-{gamma} leads to keratinocyte hyperplasia by promoting keratinocyte survival through the induction of CD40 on the surface of keratinocytes (86) and/or through the induction of Bcl-XL (87).

The absence of host-derived IFN-{gamma} was verified by the measurement of IFN-{gamma} from anti-CD3 and anti-CD28 stimulated whole cells isolated from the inflammatory lesions of animals that received IFN-{gamma}-/- T cells. As expected, we were unable to detect any measurable level of IFN-{gamma}, thus further ruling out the possibility that IFN-{gamma} might be secreted by non-T cells in the skin, including NK cells. However, we cannot rule out that very small amounts of IFN-{gamma} secreted by host cells could have inflammatory effects on donor T cells and host macrophages. Another possibility would be that in the IFN-{gamma}-/- T cell/scid transfer experiment, Th2 inflammatory T cells are generated in the absence of IFN-{gamma} that are capable of inducing psoriasiform lesions. That such immune deviation can cause disease has been recently reported in other autoimmune models that are classically associated with Th1-type inflammatory responses (88, 89). However, our data do not support this, since we were unable to detect elevated amounts of IL-4 in the supernatants of cells isolated from diseased IFN-{gamma}-/- T cell/scid animals.

In contrast to IFN-{gamma}, an absolute requirement for IL-12 in the development of chronic psoriasiform lesions in scid/scid mice was demonstrated by several observations made in our studies. First, medium and low doses of IL-12 (1 and 10 ng/mouse) administered following donor T cell transfer resulted in a higher incidence and severity of disease. Moreover, in situ staining of inflamed tissue revealed a significant present of heterodimeric IL-12 (p70), while IL-12 staining was not present at all in noninflamed control tissue. Most importantly, in vivo neutralization of IL-12 with a mAb reacting against IL-12 p70 heterodimer 7 days following T cell transfer was able to completely abrogate disease induction. An interesting aspect of our studies was that high doses of IL-12 (100 ng/mouse) actually inhibited disease induction instead of promoting disease development. This dose-dependent effect of IL-12 found in our studies are reminiscent of findings made by others in an animal model of rheumatoid arthritis (90). In this model, high doses of IL-12 for 3 wk successfully suppressed the induction of collagen induced arthritis in DBA/1 mice, while lower doses of IL-12 resulted in a more severe form of arthritis in these mice (90, 91). The reasons for these opposing effects are currently unknown.

Although our finding of the IFN-{gamma}-independent effect of IL-12 in the generation of inflammatory T cells during the onset of psoriasis are quite surprising, they are not entirely unexpected. Very recently, others have provided evidence, that IFN-{gamma} under some condition may not be crucial for the induction of other autoimmune conditions as well. For example, Simpson et al. (92) demonstrated that IFN-{gamma}-/- T cell reconstituted animals developed colitis and wasting disease at a similar rate and severity as IFN-{gamma}+/+ cell reconstituted mice. In more recent studies, Davidson et al. (93) demonstrated very nicely that IFN-{gamma} seems to be only important during the onset (acute) phase of colitis, since the administration of anti-IFN-{gamma} mAb prevented disease onset, but neutralization of IFN-{gamma} during the chronic phase had no effect on reversing colitis in IL-10 KO mice. Moreover, Segal et al. (94) showed that IL-12 is able to induce experimental allergic encephalitis (EAE) in the presence or absence of IFN-{gamma}. In an infectious disease model, IL-12 was able to exert antimicrobial activity against Leishmania donovani in IFN-{gamma}-/- mice (95). Interestingly, the leishmanicidal activity of IL-12 was dependent on TNF-{alpha} and required the activity of inducible NO synthase. Since we were able to find high levels of TNF-{alpha} in the supernatants of cells extracted from the IFN-{gamma}-/- T cell transfer scid animals, it is possible that the IL-12 disease-inducing effects in our model are also TNF-{alpha} dependent. Although our findings and above considerations point strongly toward a Th1-mediated disease mechanism, the presence of substantial amounts of IL-4 in the supernatants of cells isolated from psoriasiform lesions justify a more close look at the role of this Th2 cytokine in the disease process. It is quite possible that the pathogenesis of psoriasiform lesions in this model is dependent on both Th1 and Th2 cytokine, most likely at different stages of the disease process.

In summary, the murine chronic skin disorder described in this study included features that are normally only observed in human psoriasis, such as rete pegs, severe acanthosis, and infiltration of Th1 cells into the dermis. The clinical and histopathological abnormalities were greatly enhanced by the in vivo administration of LPS and IL-12, suggesting an important role of infectious agent(s) in the pathogenesis of the disease. Moreover, we demonstrated for the first time that the induction of psoriasiform lesions was dependent on IL-12, but independent on IFN-{gamma}. Thus, this study offers further insight into the specific pathogenic requirements of Th1 promoting cytokines and cells for the development of psoriasiform lesions and hopefully will provide further insight into the prevention and treatment of psoriasis in humans.


   Acknowledgments
 
We thank Chuck Bullock and Edwin Apilado for assistance. We also thank Alison Mullowney and Patricia Lekas for performing cell sorting and Cary Queen for comments and critical reading. Furthermore, we thank Dr. Carol Meschter (Chief Pathologist, Comparative Bioscience) for the histological evaluation of our skin samples.


   Footnotes
 
1 K.H. and A.C. contributed equally to this work. Back

2 Address correspondence and reprint requests to Dr. Rolf O. Ehrhardt, Protein Design Labs, Inc., 34801 Campus Drive, Fremont, CA 94555. E-mail address: Back

3 Abbreviations used in this paper: SEB, staphylococcal enterotoxin B; IFN-{gamma}-/-, IFN-{gamma}-deficient mice; SIL, skin infiltrating lymphocytes. Back

Received for publication January 25, 1999. Accepted for publication March 29, 1999.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Dahl, M. V. 1996. Immunodermatology. Mosby, St. Louis. 3rd Ed., pp. 301–315.
  2. Christophers, E.. 1996. The immunopathology of psoriasis. Int. Arch. Allergy Immunol. 110:199.[Medline]
  3. Barker, J. N.. 1994. The immunopathology of psoriasis. Baillieres Clin. Rheumatol. 8:429.[Medline]
  4. Boehncke, W. H.. 1996. Psoriasis and bacterial superantigens: formal or causal correlation?. Trends Microbiol. 4:485.[Medline]
  5. Prinz, J. C.. 1997. Psoriasis vulgaris, streptococci and the immune system: a riddle to be solved soon?. Scand. J. Immunol. 45:583.[Medline]
  6. Rook, G. A., J. L. Stanford. 1992. Slow bacterial infections or autoimmunity?. Immunol. Today. 13:160.[Medline]
  7. Rosenberg, E. W., P. W. Noah, Jr R. B. Skinner. 1994. Microorganisms and psoriasis. J. Natl. Med. Assoc. 86:305.[Medline]
  8. Carroll, J. M., M. R. Romero, F. M. Watt. 1995. Suprabasal integrin expression in the epidermis of transgenic mice results in developmental defects and a phenotype resembling psoriasis. Cell 83:957.[Medline]
  9. Groves, R. W., H. Mizutani, J. D. Kieffer, T. S. Kupper. 1995. Inflammatory skin disease in transgenic mice that express high levels of interleukin 1{alpha} in basal epidermis. Proc. Natl. Acad. Sci. USA 92:11874.[Abstract/Free Full Text]
  10. Wilson, J. B., W. Weinberg, R. Johnson, S. Yuspa, A. J. Levine. 1990. Expression of the BNLF-1 oncogene of Epstein-Barr virus in the skin of transgenic mice induces hyperplasia and aberrant expression of keratin 6. Cell 61:1315.[Medline]
  11. Yanagisawa, H., J. A. Richardson, J. D. Taurog, R. E. Hammer. 1995. Characterization of psoriasiform and alopecic skin lesions in HLA-B27 transgenic rats. Am. J. Pathol. 147:955.[Abstract]
  12. Bullard, D. C., K. Scharffetter-Kochanek, M. J. McArthur, J. G. Chosay, M. E. McBride, C. A. Montgomery, A. L. Beaudet. 1996. A polygenic mouse model of psoriasiform skin disease in CD18-deficient mice. Proc. Natl. Acad. Sci. USA 93:2116.[Abstract/Free Full Text]
  13. Nanney, L. B., J. P. Sundberg, L. E. King. 1996. Increased epidermal growth factor receptor in fsn/fsn mice. J. Invest. Dermatol. 106:1169.[Medline]
  14. Sundberg, J. P., M. France, D. Boggess, B. A. Sundberg, A. B. Jenson, W. G. Beamer, L. D. Shultz. 1997. Development and progression of psoriasiform dermatitis and systemic lesions in the flaky skin (fsn) mouse mutant. Pathobiology 65:271.[Medline]
  15. Schon, M. P., M. Detmar, C. M. Parker. 1997. Murine psoriasis-like disorder induced by naive CD4+ T cells. Nat. Med. 3:183.[Medline]
  16. Nickoloff, B. J., S. L. Kunkel, M. Burdick, R. M. Strieter. 1995. Severe combined immunodeficiency mouse and human psoriatic skin chimeras: validation of a new animal model. Am. J. Pathol. 146:580.[Abstract]
  17. Wrone-Smith, T., B. J. Nickoloff. 1996. Dermal injection of immunocytes induces psoriasis. J. Clin. Invest. 98:1878.[Medline]
  18. Gottlieb, S. L., P. Gilleaudeau, R. Johnson, L. Estes, T. G. Woodworth, A. B. Gottlieb, J. G. Krueger. 1995. Response of psoriasis to a lymphocyte-selective toxin (DAB389IL-2) suggests a primary immune, but not keratinocyte, pathogenic basis. Nat. Med. 1:442.[Medline]
  19. Podolsky, D. K.. 1991. Inflammatory bowel disease (I). N. Engl. J. Med. 325:928.[Medline]
  20. Taurog, J. D.. 1994. The germfree state prevents development of gut and joint inflammatory disease in HLAB2 transgenic rats. J. Exp. Med. 180:2359.[Abstract/Free Full Text]
  21. Ehrhardt, R. O., B. R. Ludviksson, B. Gray, M. Neurath, W. Strober. 1997. Induction and prevention of colonic inflammation in IL-2-deficient mice. J Immunol. 158:566.[Abstract]
  22. Kuhn, R., J. Lohler, D. Rennick, K. Rajewsky, W. Muller. 1993. Interleukin-10-deficient mice develop chronic enterocolitis. Cell 75:263.[Medline]
  23. Mombaerts, P., E. Mizoguchi, M. J. Grusby, L. H. Glimcher, A. K. Bhan, S. Tonegawa. 1993. Spontaneous development of inflammatory bowel disease in T cell receptor mutant mice. Cell 75:274.[Medline]
  24. Schultz, M., R. Sellon, S. Tonkonogy, E. Balish, R. Sartor. 1997. IL-2 deficient mice raised under germ-free conditions develop delayed mild focal intestinal inflammation and progressive loss of B cells. Gastroenterology 112:1086.
  25. Aranda, R., B. C. Sydora, P. L. McAllister, S. W. Binder, H. Y. Yang, S. R. Targan, M. Kronenberg. 1997. Analysis of intestinal lymphocytes in mouse colitis mediated by transfer of CD4+, CD45RBhigh T cells to SCID recipients. J Immunol. 158:3464.[Abstract]
  26. Rath, H. C., H. H. Herfarth, J. S. Ikeda, W. B. Grenther, Jr T. E. Hamm, E. Balish, J. D. Taurog, R. E. Hammer, K. H. Wilson, R. B. Sartor. 1996. Normal luminal bacteria, especially Bacteroides species, mediate chronic colitis, gastritis, and arthritis in HLA-B27/human ß2 microglobulin transgenic rats. J Clin Invest. 98:945.[Medline]
  27. Shomer, N. H., C. A. Dangler, M. D. Schrenzel, J. G. Fox. 1997. Helicobacter bilis-induced inflammatory bowel disease in scid mice with defined flora. Infect. Immun. 65:4858.[Abstract]
  28. Cahill, R. J., C. J. Foltz, J. G. Fox, C. A. Dangler, F. Powrie, D. B. Schauer. 1997. Inflammatory bowel disease: an immunity-mediated condition triggered by bacterial infection with Helicobacter hepaticus. Infect. Immun. 65:3126.[Abstract]
  29. Finn, A., S. Strobel, M. Levin, N. Klein. 1994. Endotoxin-induced neutrophil adherence to endothelium: relationship to CD11b/CD18 and L-selectin expression and matrix disruption. Ann. NY Acad. Sci. 725:173.[Medline]
  30. Lynam, E. B., S. I. Simon, Y. P. Rochon, L. A. Sklar. 1994. Lipopolysaccharide enhances CD11b/CD18 function but inhibits neutrophil aggregation. Blood 83:3303.[Abstract/Free Full Text]
  31. Crockett-Torabi, E., B. Sulenbarger, C. W. Smith, J. C. Fantone. 1995. Activation of human neutrophils through L-selectin and Mac-1 molecules. J. Immunol. 154:2291.[Abstract]
  32. Spertini, O., F. W. Luscinskas, G. S. Kansas, J. M. Munro, J. D. Griffin, Jr M. A. Gimbrone, T. F. Tedder. 1991. Leukocyte adhesion molecule-1 (LAM-1, L-selectin) interacts with an inducible endothelial cell ligand to support leukocyte adhesion. J. Immunol. 147:2565.[Abstract/Free Full Text]
  33. Neumann, B., B. Engelhardt, H. Wagner, B. Holzmann. 1997. Induction of acute inflammatory lung injury by staphylococcal enterotoxin B. J. Immunol. 158:1862.[Abstract]
  34. Krakauer, T.. 1994. Cell adhesion molecules are co-receptors for staphylococcal enterotoxin B-induced T-cell activation and cytokine production. Immunol. Lett. 39:121.[Medline]
  35. Mehindate, K., R. al-Daccak, F. Damdoumi, W. Mourad. 1996. Synergistic effect between CD40 and class II signals overcome the requirement for class II dimerization in superantigen-induced cytokine gene expression. Eur. J. Immunol. 26:2075.[Medline]
  36. Trinchieri, G.. 1998. Proinflammatory and immunoregulatory functions of interleukin-12. Int. Rev. Immunol. 16:365.[Medline]
  37. Segal, B. M., D. M. Klinman, E. M. Shevach. 1997. Microbial products induce autoimmune disease by an IL-12-dependent pathway. J. Immunol. 158:5087.[Abstract]
  38. Neurath, M. F., I. Fuss, B. L. Kelsall, E. Stuber, W. Strober. 1995. Antibodies to interleukin 12 abrogate established experimental colitis in mice. J. Exp. Med. 182:1281.[Abstract/Free Full Text]
  39. Tarrant, T. K., P. B. Silver, C. C. Chan, B. Wiggert, R. R. Caspi. 1998. Endogenous IL-12 is required for induction and expression of experimental autoimmune uveitis. J. Immunol. 161:122.[Abstract/Free Full Text]
  40. Gately, M. K., L. M. Renzetti, J. Magram, A. S. Stern, L. Adorini, U. Gubler, D. H. Presky. 1998. The interleukin-12/interleukin-12-receptor system: role in normal and pathologic immune responses. Annu. Rev. Immunol. 16:495.[Medline]
  41. Okura, Y., K. Takeda, S. Honda, H. Hanawa, H. Watanabe, M. Kodama, T. Izumi, Y. Aizawa, S. Seki, T. Abo. 1998. Recombinant murine interleukin-12 facilitates induction of cardiac myosin-specific type 1 helper T cells in rats. Circ. Res. 82:1035.[Abstract/Free Full Text]
  42. Trembleau, S., T. Germann, M. K. Gately, L. Adorini. 1995. The role of IL-12 in the induction of organ-specific autoimmune diseases. Immunol. Today 16:383.[Medline]
  43. Billiau, A.. 1996. Interferon-{gamma} in autoimmunity. Cytokine Growth Factor Rev. 7:25.[Medline]
  44. Vollmer, S., A. Menssen, P. Trommler, D. Schendel, J. C. Prinz. 1994. T lymphocytes derived from skin lesions of patients with psoriasis vulgaris express a novel cytokine pattern that is distinct from that of T helper type 1 and T helper type 2 cells. Eur. J. Immunol. 24:2377.[Medline]
  45. Schlaak, J. F., M. Buslau, W. Jochum, E. Hermann, M. Girndt, H. Gallati, K. H. Meyer zum Buschenfelde, B. Fleischer. 1994. T cells involved in psoriasis vulgaris belong to the Th1 subset. J. Invest. Dermatol. 102:145.[Medline]
  46. Prinz, J. C., B. Gross, S. Vollmer, P. Trommler, I. Strobel, M. Meurer, G. Plewig. 1994. T cell clones from psoriasis skin lesions can promote keratinocyte proliferation in vitro via secreted products. Eur. J. Immunol. 24:593.[Medline]
  47. Romagnani, P., F. Annunziato, M. C. Baccari, P. Parronchi. 1997. T cells and cytokines in Crohn’s disease. Curr. Opin. Immunol. 9:793.[Medline]
  48. Nickoloff, B. J., T. Wrone-Smith. 1997. Animal models of psoriasis. Nat. Med. 3:475.[Medline]
  49. Nicolas, J. F., N. Chamchick, J. Thivolet, J. Wijdenes, P. Morel, J. P. Revillard. 1991. CD4 antibody treatment of severe psoriasis. Lancet 338:321.[Medline]
  50. Prinz, J., O. Braun-Falco, M. Meurer, P. Daddona, C. Reiter, P. Rieber, G. Riethmuller. 1991. Chimaeric CD4 monoclonal antibody in treatment of generalised pustular psoriasis. Lancet 338:320.[Medline]
  51. Rizova, H., J. F. Nicolas, P. Morel, J. Kanitakis, A. Demidem, J. P. Revillard, J. Wijdenes, J. Thivolet, D. Schmitt. 1994. The effect of anti-CD4 monoclonal antibody treatment on immunopathological changes in psoriatic skin. J. Dermatol. Sci. 7:1.[Medline]
  52. Morel, P., J. P. Revillard, J. F. Nicolas, J. Wijdenes, H. Rizova, J. Thivolet. 1992. Anti-CD4 monoclonal antibody therapy in severe psoriasis. J. Autoimmun. 5:465.[Medline]
  53. Schafer, R., J. M. Sheil. 1995. Superantigens and their role in infectious disease. Adv. Pediatr. Infect. Dis. 10:369.[Medline]
  54. Valdimarsson, H., H. Sigmundsdottir, I. Jonsdottir. 1997. Is psoriasis induced by streptococcal superantigens and maintained by M-protein-specific T cells that cross-react with keratin?. Clin. Exp. Immunol. 107:(Suppl. 1):21.[Medline]
  55. Tagami, H.. 1997. Triggering factors. Clin. Dermatol. 15:677.[Medline]
  56. Boehncke, W. H., T. M. Zollner, D. Dressel, R. Kaufmann. 1997. Induction of psoriasiform inflammation by a bacterial superantigen in the SCID-hu xenogeneic transplantation model. J. Cutan. Pathol. 24:1.[Medline]
  57. Prens, E., R. Debets, J. Hegmans. 1995. T lymphocytes in psoriasis. Clin Dermatol. 13:115.[Medline]
  58. Christofidou-Solomidou, M., S. M. Albelda, F. C. Bennett, G. F. Murphy. 1997. Experimental production and modulation of human cytotoxic dermatitis in human-murine chimeras. Am. J. Pathol. 150:631.[Abstract]
  59. Austin, L. M., T. R. Coven, N. Bhardwaj, R. Steinman, J. G. Krueger. 1998. Intraepidermal lymphocytes in psoriatic lesions are activated GMP-17(TIA-1)+CD8+CD3+ CTLs as determined by phenotypic analysis. J. Cutan. Pathol. 25:79.[Medline]
  60. Onuma, S.. 1994. Immunohistochemical studies of infiltrating cells in early and chronic lesions of psoriasis. J. Dermatol. 21:223.[Medline]
  61. Krueger, J. G., J. T. Wolfe, R. T. Nabeya, V. P. Vallat, P. Gilleaudeau, N. S. Heftler, L. M. Austin, A. B. Gottlieb. 1995. Successful ultraviolet B treatment of psoriasis is accompanied by a reversal of keratinocyte pathology and by selective depletion of intraepidermal T cells. J. Exp. Med. 182:2057.[Abstract/Free Full Text]
  62. Baker, B. S., A. V. Powles, S. Lambert, H. Valdimarsson, L. Fry. 1988. A prospective study of the Koebner reaction and T lymphocytes in uninvolved psoriatic skin. Acta Derm. Venereol. 68:430.[Medline]
  63. D’Andrea, A., M. Aste-Amezaga, N. M. Valiante, X. Ma, M. Kubin, G. Trinchieri. 1993. Interleukin 10 (IL-10) inhibits human lymphocyte interferon-{gamma} production by suppressing natural killer cell stimulatory factor/IL-12 synthesis in accessory cells. J. Exp. Med. 178:1041.[Abstract/Free Full Text]
  64. Gazzinelli, R. T., S. Hieny, T. A. Wynn, S. Wolf, A. Sher. 1993. Interleukin 12 is required for the T-lymphocyte-independent induction of interferon {gamma} by an intracellular parasite and induces resistance in T-cell-deficient hosts. Proc. Natl. Acad. Sci. USA 90:6115.[Abstract/Free Full Text]
  65. Hunter, C. A., R. Chizzonite, J. S. Remington. 1995. IL-1 beta is required for IL-12 to induce production of IFN-{gamma} by NK cells: a role for IL-1ß in the T cell-independent mechanism of resistance against intracellular pathogens. J. Immunol. 155:4347.[Abstract]
  66. Jacob, T., P. S. Walker, A. M. Krieg, M. C. Udey, J. C. Vogel. 1998. Activation of cutaneous dendritic cells by CpG-containing oligodeoxynucleotides: a role for dendritic cells in the augmnetation of Th1 responses by immunostimulatory DNA. J. Immunol. 161:3042.[Abstract/Free Full Text]
  67. Pober, J. S., R. S. Cotran. 1990. Cytokines and endothelial cell biology. Physiol. Rev. 70:427.[Free Full Text]
  68. Bevilacqua, M. P.. 1993. Endothelial-leukocyte adhesion molecules. Annu. Rev. Immunol. 11:767.[Medline]
  69. Leung, D. Y., M. Gately, A. Trumble, B. Ferguson-Darnell, P. M. Schlievert, L. J. Picker. 1995. Bacterial superantigens induce T cell expression of the skin-selective homing receptor, the cutaneous lymphocyte-associated antigen, via stimulation of interleukin 12 production. J. Exp. Med. 181:747.[Abstract/Free Full Text]
  70. Picker, L. J., S. A. Michie, L. S. Rott, E. C. Butcher. 1990. A unique phenotype of skin-associated lymphocytes in humans: preferential expression of the HECA-452 epitope by benign and malignant T cells at cutaneous sites. Am. J. Pathol. 136:1053.[Abstract]
  71. Picker, L. J., T. K. Kishimoto, C. W. Smith, R. A. Warnock, E. C. Butcher. 1991. ELAM-1 is an adhesion molecule for skin-homing T cells. Nature 349:796.[Medline]
  72. Berg, E. L., T. Yoshino, L. S. Rott, M. K. Robinson, R. A. Warnock, T. K. Kishimoto, L. J. Picker, E. C. Butcher. 1991. The cutaneous lymphocyte antigen is a skin lymphocyte homing receptor for the vascular lectin endothelial cell-leukocyte adhesion molecule 1. J. Exp. Med. 174:1461.[Abstract/Free Full Text]
  73. Schattner, A.. 1994. Lymphokines in autoimmunity: a critical review. Clin. Immunol. Immunopathol. 70:177.[Medline]
  74. Barna, M., F. G. Snijdewint, F. L. van der Heijden, J. D. Bos, M. L. Kapsenberg. 1994. Characterization of lesional psoriatic skin T lymphocyte clones. Acta Derm. Venereol. Suppl. 186:9.[Medline]
  75. Scheynius, A., J. Fransson, C. Johansson, H. Hammar, B. Baker, L. Fry, H. Valdimarsson. 1992. Expression of interferon-{gamma} receptors in normal and psoriatic skin. J. Invest. Dermatol. 98:255.[Medline]
  76. Yamamoto, T., M. Matsuuchi, I. Katayama, K. Nishioka. 1998. Repeated subcutaneous injection of staphylococcal enterotoxin B- stimulated lymphocytes retains epidermal thickness of psoriatic skin-graft onto severe combined immunodeficient mice. J. Dermatol. Sci. 17:8.[Medline]
  77. Lemster, B. H., P. B. Carroll, H. R. Rilo, N. Johnson, A. Nikaein, A. W. Thomson. 1995. IL-8/IL-8 receptor expression in psoriasis and the response to systemic tacrolimus (FK506) therapy. Clin. Exp. Immunol. 99:148.[Medline]
  78. Gearing, A. J., N. J. Fincham, C. R. Bird, M. Wadhwa, A. Meager, J. E. Cartwright, R. D. Camp. 1990. Cytokines in skin lesions of psoriasis. Cytokine 2:68.[Medline]
  79. Uyemura, K., M. Yamamura, D. F. Fivenson, R. L. Modlin, B. J. Nickoloff. 1993. The cytokine network in lesional and lesion-free psoriatic skin is characterized by a T-helper type 1 cell-mediated response. J. Invest. Dermatol. 101:701.[Medline]
  80. Nestle, F. O., L. A. Turka, B. J. Nickoloff. 1994. Characterization of dermal dendritic cells in psoriasis: Autostimulation of T lymphocytes and induction of Th1 type cytokines. J. Clin. Invest. 94:202.
  81. Sigmundsdottir, H., B. Sigurgeirsson, M. Troye-Blomberg, M. F. Good, H. Valdimarsson, I. Jonsdottir. 1997. Circulating T cells of patients with active psoriasis respond to streptococcal M-peptides sharing sequences with human epidermal keratins. Scand. J. Immunol. 45:688.[Medline]
  82. Saunders, N., A. Dahler, S. Jones, R. Smith, A. Jetten. 1996. Interferon-{gamma} as a regulator of squamous differentiation. J. Dermatol. Sci. 13:98.[Medline]
  83. Fransson, J., Q. Shen, A. Scheynius, H. Hammar. 1996. The effect of IFN-{gamma} on healthy and psoriatic keratinocytes in a skin equivalent model is influenced by the source of the keratinocytes and by their interactions with fibroblasts. Arch. Dermatol. Res. 289:14.[Medline]
  84. Kaneko, F., M. Suzuki, Y. Takiguchi, N. Itoh, T. Minagawa. 1990. Immunohistopathologic studies in the development of psoriatic lesion influenced by {gamma}-interferon and the producing cells. J. Dermatol. Sci. 1:425.[Medline]
  85. Nickoloff, B. J., R. S. Mitra, J. T. Elder, G. J. Fisher, J. J. Voorhees. 1989. Decreased growth inhibition by recombinant {gamma} interferon is associated with increased transforming growth factor-{alpha} production in keratinocytes cultured from psoriatic lesions. Br. J. Dermatol. 121:161.[Medline]
  86. Denfeld, R. W., D. Hollenbaugh, A. Fehrenbach, J. M. Weiss, A. von Leoprechting, B. Mai, U. Voith, E. Schopf, A. Aruffo, J. C. Simon. 1996. CD40 is functionally expressed on human keratinocytes. Eur. J. Immunol. 26:2329.[Medline]
  87. Wrone-Smith, T., T. Johnson, B. Nelson, L. H. Boise, C. B. Thompson, G. Nunez, B. J. Nickoloff. 1995. Discordant expression of Bcl-x and Bcl-2 by keratinocytes in vitro and psoriatic keratinocytes in vivo. Am. J. Pathol. 146:1079.[Abstract]
  88. Lafaille, J. J., F. V. Keere, A. L. Hsu, J. L. Baron, W. Haas, C. S. Raine, S. Tonegawa. 1997. Myelin basic protein-specific T helper 2 (Th2) cells cause experimental autoimmune encephalomyelitis in immunodeficient hosts rather than protect them from the disease. J. Exp. Med. 186:307.[Abstract/Free Full Text]
  89. Pakala, S. V., M. O. Kurrer, J. D. Katz. 1997. T helper 2 (Th2) T cells induce acute pancreatitis and diabetes in immune-compromised nonobese diabetic (NOD) mice. J. Exp. Med. 186:299.[Abstract/Free Full Text]
  90. Hess, H., M. K. Gately, E. Rude, E. Schmitt, J. Szeliga, T. Germann. 1996. High doses of interleukin-12 inhibit the development of joint disease in DBA/1 mice immunized with type II collagen in complete Freund’s adjuvant. Eur. J. Immunol. 26:187.[Medline]
  91. Germann, T., J. Szeliga, H. Hess, S. Storkel, F. J. Podlaski, M. K. Gately, E. Schmitt, E. Rude. 1995. Administration of interleukin 12 in combination with type II collagen induces severe arthritis in DBA/1 mice. Proc. Natl. Acad. Sci. USA 92:4823.[Abstract/Free Full Text]
  92. Simpson, S. J., S. Shah, M. Comiskey, Y. P. de Jong, B. Wang, E. Mizoguchi, A. K. Bhan, C. Terhorst. 1998. T cell-mediated pathology in two models of experimental colitis depends predominantly on the interleukin 12/signal transducer and activator of transcription (Stat)-4 pathway, but is not conditional on interferon {gamma} expression by T cells. J. Exp. Med. 187:1225.[Abstract/Free Full Text]
  93. Davidson, N. J., S. A. Hudak, R. E. Lesley, S. Menon, M. W. Leach, D. M. Rennick. 1998. IL-12, but not IFN-{gamma}, plays a major role in sustaining the chronic phase of colitis in IL-10-deficient mice. J. Immunol. 161:3143.[Abstract/Free Full Text]
  94. Segal, B. M., B. K. Dwyer, E. M. Shevach. 1998. An interleukin (IL)-10/IL-12 immunoregulatory circuit controls susceptibility to autoimmune disease. J. Exp. Med. 187:537.[Abstract/Free Full Text]
  95. Taylor, A. P., H. W. Murray. 1997. Intracellular antimicrobial activity in the absence of interferon-{gamma}: effect of interleukin-12 in experimental visceral leishmaniasis in interferon-{gamma} gene-disrupted mice. J. Exp. Med. 185:1231.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Vet PatholHome page
D. M. Danilenko
Review Paper: Preclinical Models of Psoriasis
Vet. Pathol., July 1, 2008; 45(4): 563 - 575.
[Abstract] [Full Text] [PDF]

Home page
 Arch DermatolHome page
A. B. Kimball, K. B. Gordon, R. G. Langley, A. Menter, E. K. Chartash, J. Valdes, and for the ABT-874 Psoriasis Study Investigators
Safety and Efficacy of ABT-874, a Fully Human Interleukin 12/23 Monoclonal Antibody, in the Treatment of Moderate to Severe Chronic Plaque Psoriasis: Results of a Randomized, Placebo-Controlled, Phase 2 Trial
Arch Dermatol, February 1, 2008; 144(2): 200 - 207.
[Abstract] [Full Text] [PDF]

Home page
 NEJMHome page
G. G. Krueger, R. G. Langley, C. Leonardi, N. Yeilding, C. Guzzo, Y. Wang, L. T. Dooley, M. Lebwohl, and the CNTO 1275 Psoriasis Study Group
A Human Interleukin-12/23 Monoclonal Antibody for the Treatment of Psoriasis
N. Engl. J. Med., February 8, 2007; 356(6): 580 - 592.
[Abstract] [Full Text] [PDF]

Home page
 BloodHome page
Y. Wada, R. Lu, D. Zhou, J. Chu, T. Przewloka, S. Zhang, L. Li, Y. Wu, J. Qin, V. Balasubramanyam, et al.
Selective abrogation of Th1 response by STA-5326, a potent IL-12/IL-23 inhibitor
Blood, February 1, 2007; 109(3): 1156 - 1164.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
F. Leon, N. Contractor, I. Fuss, T. Marth, E. Lahey, S. Iwaki, A. la Sala, V. Hoffmann, W. Strober, and B. L. Kelsall
Antibodies to Complement Receptor 3 Treat Established Inflammation in Murine Models of Colitis and a Novel Model of Psoriasiform Dermatitis
J. Immunol., November 15, 2006; 177(10): 6974 - 6982.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
E. Toichi, G. Torres, T. S. McCormick, T. Chang, M. A. Mascelli, C. L. Kauffman, N. Aria, A. B. Gottlieb, D. E. Everitt, B. Frederick, et al.
An Anti-IL-12p40 Antibody Down-Regulates Type 1 Cytokines, Chemokines, and IL-12/IL-23 in Psoriasis
J. Immunol., October 1, 2006; 177(7): 4917 - 4926.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
G. Piskin, R. M. R. Sylva-Steenland, J. D. Bos, and M. B. M. Teunissen
In Vitro and In Situ Expression of IL-23 by Keratinocytes in Healthy Skin and Psoriasis Lesions: Enhanced Expression in Psoriatic Skin
J. Immunol., February 1, 2006; 176(3): 1908 - 1915.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
K. Hong, E. L. Berg, and R. O. Ehrhardt
Persistence of Pathogenic CD4+ Th1-Like Cells In Vivo in the Absence of IL-12 but in the Presence of Autoantigen
J. Immunol., April 1, 2001; 166(7): 4765 - 4772.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
M. P. Schon, M. Schon, H. B. Warren, J. P. Donohue, and C. M. Parker
Cutaneous Inflammatory Disorder in Integrin {alpha}E (CD103)-Deficient Mice
J. Immunol., December 1, 2000; 165(11): 6583 - 6589.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
A. Chu, K. Hong, E. L. Berg, and R. O. Ehrhardt
Tissue Specificity of E- and P-Selectin Ligands in Th1-Mediated Chronic Inflammation
J. Immunol., November 1, 1999; 163(9): 5086 - 5093.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hong, K.
Right arrow Articles by Ehrhardt, R. O.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hong, K.
Right arrow Articles by Ehrhardt, R. O.
Right arrowPubmed/NCBI databases
*Gene*GEO Profiles
*HomoloGene*UniGene
*Compound via MeSH
*Substance via MeSH
Medline Plus Health Information
*Psoriasis

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS