|
|
||||||||


* Department of Dermatology,
Institute for Advanced Medical Research, and
Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan
| Abstract |
|---|
|
|
|---|
in vivo suppressed IgG anti-Dsg3 Ab production and the PV phenotype, indicating a pathogenic role of IL-4. This strategy is useful for evaluating the effector function of autoreactive T cells involved in the pathogenesis of various autoimmune diseases. | Introduction |
|---|
|
|
|---|
Pemphigus vulgaris (PV)3 is a life-threatening blistering disease involving IgG autoantibodies directed against desmoglein 3 (Dsg3). Dsg3 is a cadherin-type glycoprotein expressed on stratified squamous epithelium, including the skin and oral mucosa, and plays a critical role in cell-cell adhesion (5). Anti-Dsg3 autoantibodies bind to keratinocyte cell surfaces and induce cell detachment, resulting in blisters and erosions in the skin and mucous membranes as well as characteristic histological findings, such as suprabasilar acantholysis (6, 7). Dsg3-reactive CD4+ T cells have been detected and characterized in PV patients and healthy individuals, but it remains unclear whether these autoreactive T cells can induce the PV phenotype in vivo. In this study, we developed a novel experimental system that evaluates the in vivo pathogenicity of individual Dsg3-reactive T cell clones. In this system, Dsg3-reactive T cell lines generated in vitro from Dsg3–/– mice were adoptively transferred into recipient immunodeficient Rag-2–/– mice (Dsg3+/+) to examine whether T cell lines have the ability to induce the PV phenotype after adoptive transfer. Using this system, we identified IL-4 as a critical T cell-derived factor involved in the pathogenesis of PV.
| Materials and Methods |
|---|
|
|
|---|
Dsg3–/– mice with a mixed genetic background of 129/SV (H-2b) and C57BL/6J (H-2b) were obtained by mating male and female Dsg3–/– mice (The Jackson Laboratory) (8). C57BL/6 mice and C57BL/6 Rag-2–/– mice were purchased from the Central Institute for Experimental Animals (Tokyo, Japan). OT-II (OVA-specific) TCR transgenic mice (H-2b) were originally generated by Barnden et al. (9), and Rag-2–/– OT-II transgenic mice (H-2b) were kindly provided by Prof. S. Koyasu (Keio University). The Keio University Ethics Committee for Animal Experiments approved all experiments in this study.
Antigens
A baculoprotein rDsg3EHis, which includes the extracellular domain of mouse Dsg3 (amino acid residues 1–565), an E-tag, and a His-tag, was produced as described previously (10) with some modifications. In brief, the purification was improved by serial procedures using Talon affinity metal resin (Clontech Laboratories) followed by a HiTrap anti-E Tag column (GE Healthcare). Five mouse Dsg3 fragments (rDsg3-1–5) expressed in Escherichia coli were prepared as soluble maltose-binding protein (MalBP)-Dsg3 fusion proteins as described (11). The Dsg3 fragments encompassing together the entire 565-aa sequence of the extracellular domain of mouse Dsg3 included rDsg3-1 (aa 1–119), rDsg3-2 (aa 99–230), rDsg3-3 (aa 210–345), rDsg3-4 (aa 325–455), and rDsg3-5 (aa 428–565). These recombinant proteins were dialyzed against PBS containing 0.5 mM CaCl2, filter-sterilized, and stored at –80°C until use. The expression of recombinant Dsg3 fragments was evaluated by SDS-PAGE followed by Coomassie blue staining or immunoblotting probed with an anti-mouse Dsg3 mAb (AK7 or AK18) (7).
Recombinant adenovirus harboring Dsg3 and soluble cytokine receptors
Adenoviral vectors harboring the entire extracellular domain and transmembrane region of mouse Dsg3 (rDsg3
IC; aa 1–590) or the extracellular domain of cytokine receptors (IL-4R
, IL-10R
, and IFN-
R1) were constructed using the AdEasy adenoviral vector system (Stratagene) according to the manufacturers instructions. rDsg3
IC was adenovirally expressed in COS cells, which were subjected to sonication in PBS containing 0.5 mM CaCl2 and 0.01% Triton X-100. The cellular lysates were filter-sterilized and used in T cell cultures as a source of Dsg3. The expression of Dsg3 was evaluated by SDS-PAGE followed by immunoblotting with anti-mouse Dsg3 mAb and rabbit anti-actin polyclonal Ab (Sigma-Aldrich). For soluble cytokine receptors, the cDNA for the entire extracellular domain of each cytokine receptor was cloned from a spleen cDNA library and used to construct recombinant adenoviruses. Each recombinant adenovirus harboring a soluble cytokine receptor was concentrated by CsCl2 density gradient centrifugation, dialyzed against PBS, and stocked at –80°C until use. The in vivo expression of soluble cytokine receptors was confirmed by immunoblotting plasma obtained from adenovirus-infected mice with goat anti-IL-4R
, anti-IL-10R
, or anti-IFN-
R1 polyclonal Abs (R&D Systems).
Ag-specific T cell lines
Footpads of Dsg3–/– mice were immunized with 5 µg of rDsg3EHis emulsified with CFA (Sigma-Aldrich). After 7 days, a single-cell suspension (3 x 106/well) was prepared from the popliteal lymph nodes and cultured in 24-well plates with a mixture of rDsg3-1–5 (5 µg/ml each) in complete medium (RPMI 1640, 2 mM L-glutamine, 1 mM pyruvate, 50 U/ml penicillin, and 50 µg/ml streptomycin) supplemented with 1% C57BL/6 mouse serum. The cells were stimulated twice with the mixture of rDsg3-1–5 in the presence of 106 autologous 40 Gy-irradiated splenocytes in complete medium containing 10% FBS (Cambrex). T-STIM without Con A (BD Biosciences) was added to a final concentration of 1% twice a week as a source of growth factors. T cell blasts were subsequently subjected to limiting dilution using round-bottom 96-well plates in the presence of irradiated autologous splenocytes (2 x 104/well), antigenic Dsg3 fragments, and 1% T-STIM without Con A.
T cell proliferation assay
Dsg3-specific T cell proliferation was measured by [3H]thymidine uptake as described (11). In some experiments, bone marrow-derived dendritic cells, which were prepared by culturing C57BL/6 bone marrow cells with 10 ng/ml GM-CSF (PeproTech) for 7 days, were used as APCs. Before the coculture with T cells, the bone marrow-derived dendritic cells were pulsed with pAd-rDsg3
IC or mock vector-transduced COS cell lysates (100 µg/ml) and maturated with 10 µg/ml LPS (Sigma-Aldrich) for 24 h. MHC class II restriction was determined by evaluating the inhibitory effect on Ag-induced T cell proliferation of 4 µg/ml rat anti-I-Ab mAb (clone M5/114; BD Biosciences). An isotype-matched rat mAb to an irrelevant Ag (BD Biosciences) was used as a control.
Passive transfer
To evaluate the pathogenicity of Dsg3-reactive T cell lines, Dsg3-reactive T cell lines (106) and splenic Dsg3–/– B cells (5 x 106) were transferred into Rag-2–/– mice via the tail vein. In vivo-primed Dsg3–/– B cells were prepared by depleting CD4+ and CD8+ cells from the splenocytes of rDsg3EHis-immunized Dsg3–/– mice (10), followed by the positive selection of B220+ cells using the MACS cell separation system (Miltenyi Biotec). A portion of the separated CD4+ and CD8+ cells was used as unfractionated Dsg3–/– T cells. In some experiments, recombinant adenovirus harboring sIL-4R
, sIL-10R
, or sIFN-
R1 (109 infections units) was directly injected into Rag-2–/– mice via tail vein 5 days before the passive transfer of pathogenic Dsg3-reactive T cell clones and Dsg3–/–-primed B cells. It has been demonstrated that recombinant adenovirus injected from tail vein mainly infects hepatocytes, resulting in expression of recombinant protein (12).
RT-PCR
T cell lines were stimulated with 25 ng/ml PMA (Sigma-Aldrich) and 1 µg/ml ionomycin (Sigma-Aldrich) for 3 days, and isolated using anti-CD4 mAb-coupled magnetic beads (Dynal Biotech). Total RNA was isolated from individual T cell lines using the RNeasy mini kit with RNase-free DNase (Qiagen). For the analysis of TCR Vβ gene usage, aliquots of the synthesized cDNA (5 ng of total RNA equivalent) were amplified using a panel of TCR Vβ region-specific primers in combination with a Cβ region primer for 37 cycles. Primers for Vβ1–20 and Cβ were designed based on previous reports (13, 14, 15). The expression of cytokines and chemokine receptors was also examined by PCR using the specific primers listed in Table I for 38 and 40 cycles, respectively.
|
Surface markers of the Dsg3-reactive T cell lines were analyzed using FITC-conjugated anti-mouse CD4 mAb (clone GK1.5), FITC-conjugated anti-mouse CD8 mAb (clone 53-6.7), PE-conjugated anti-mouse TCRβ mAb (clone H57-597), and Cy-Chrome-conjugated anti-mouse CD4 mAb (clone H129.19), all of which were purchased from BD Biosciences. In some experiments, T cell lines labeled with 1 µM CFSE (Molecular Probes) were analyzed by flow cytometry after gating on the CD4+TCRβ+ population of the lymphocyte fraction.
Anti-Dsg3 Ab
IgG anti-Dsg3 Abs in plasma samples or culture supernatants were quantitatively measured using an ELISA as described previously (10). To examine the capacity of B cells to produce anti-Dsg3 Abs in vitro, MACS-sorted Dsg3–/– B cells were cultured with 500 ng/ml soluble CD40L (R&D Systems) in the presence of various concentrations of IL-4, IL-10, or IFN-
(R&D Systems) for 7 days.
Histopathology
Formalin-fixed palate tissue was stained with H&E and observed with an inverted microscope TE2000-U (Nikon).
Immunohistochemistry
For direct immunofluorescent staining, 10-µm cryosections of the palate were directly stained with AlexaFluor 488-conjugated anti-mouse IgG Abs (Molecular Probes) and observed using a fluorescence microscope (Nikon) to detect IgG deposits. For indirect staining, 6-µm cryosections of the spleen were fixed with acetone and subsequently stained with the appropriate combination of the following Abs: FITC-conjugated anti-mouse CD19 (clone 1D3), PE-conjugated anti-mouse TCRβ (clone H57-597), AlexaFluor 488-conjugated anti-mouse B220 (clone RA3-6B2), biotinylated anti-mouse CD4 (clone RM4-5, BD Biosciences), and anti-Ki-67 mAb (clone TEC-3; DakoCytomation). Secondary Abs included AlexaFluor 488-conjugated anti-mouse IgG, AlexaFluor 660-conjugated anti-rat IgG, and AlexaFluor 488-conjugated anti-FITC Abs, and AlexaFluor 568-conjugated streptavidin (Molecular Probes). BrdU staining was performed using AlexaFluor 660-conjugated anti-BrdU mAb (clone PRB-1, Molecular Probes), as previously described (16). Sections were observed under a confocal laser fluorescence microscope FV1000 (Olympus).
Statistical analysis
All continuous data are shown as the means ± SD. Two-tailed repeated-measures ANOVA, Fishers exact probability test, or the Mann-Whitney U test was used as appropriate.
| Results |
|---|
|
|
|---|
We prepared recombinant mouse Dsg3 fragments using three different expression systems (Fig. 1A). rDsg3EHis (10), a baculoprotein containing the entire extracellular domain of Dsg3, was used to immunize Dsg3–/– mice. rDsg3-1–5, a series of recombinant MalBP-Dsg3 fusion proteins produced in E. coli, were used to expand Dsg3-reactive T cells and to evaluate antigenic regions in vitro. The purity of each recombinant protein was >95% (Fig. 1B). Lysates from COS cells infected with pAd-rDsg3
IC, an adenovirus vector harboring Dsg3 cDNA lacking the sequence for the intracellular domain, were used to evaluate T cell reactivity to native Dsg3 produced in mammalian cells (Fig. 1C). Serial use of more than one Dsg3 preparation for T cell stimulation is useful to eliminate expansion of T cells responsive to contaminant proteins unique to individual Ag preparations.
|
To establish Dsg3-reactive T cell lines, the footpads of Dsg3–/– mice were immunized with rDsg3EHis emulsified with CFA. Single-cell suspensions of lymphocytes were prepared from the popliteal lymph nodes and were subsequently stimulated twice with a mixture of rDsg3-1–5 in vitro. The expanded cells that showed a specific proliferative response to at least one of the Dsg3 fragments were subjected to limiting dilution. From this selection, we obtained 59 T cell lines that were specifically reactive with one of rDsg3-1–4. All of these T cell lines were restricted by MHC class II (Fig. 2A) and expressed the CD4 surface marker (Fig. 2B). To evaluate whether these T cell lines responded to peptides generated from native Dsg3 through Ag processing, randomly selected T cell lines were cultured with bone marrow-derived dendritic cells pulsed with pAd-rDsg3
IC-infected and control adenovirus-infected cell lysates. All the T cell lines examined showed a specific response to Dsg3-expressing cell lysates in a MHC class II-dependent manner (Fig. 2C). The in vitro-generated T cell lines were reactive to two different Dsg3 preparations, indicating that they were specific for Dsg3. Eighteen Dsg3-reactive T cell lines were confirmed to be clones based on their expression of a single functional TCR Vβ-chain, determined by family PCR combined with a direct nucleotide sequencing (Fig. 2D).
|
Twenty Dsg3-reactive T cell lines, including 13 clones expressing single functional TCR Vβ-chain, were further evaluated for their in vivo pathogenicity. Since our previous study demonstrated that splenic T cells and B cells are required to induce experimental PV (17), the individual T cell lines were transferred into Rag-2–/– mice together with primed B cells isolated from the spleen of a rDsg3EHis-immunized Dsg3–/– mouse. In a representative experiment, clone 154#33 effectively promoted the production of IgG anti-Dsg3 Abs in vivo (Fig. 3A) and subsequently induced a PV phenotype, consisting of skin erosions and hair loss (Fig. 3B). Mice into which clone 154#33 was transferred showed acantholytic blisters and in vivo IgG deposition on keratinocyte cell surfaces (Fig. 3C). These PV features were also observed in positive control mice, into which unfractionated Dsg3–/– T cells had been transferred instead of Dsg3-reactive T cell lines. In contrast, transplantation of another clone, 152#25, failed to induce the IgG anti-Dsg3 Ab production or the PV phenotype, indicating that only a subset of the Dsg3-reactive T cell lines possessed in vivo pathogenic activity. The PV phenotype was not observed in control mice that received primed Dsg3–/– B cells alone or in combination with irrelevant OVA-specific T cells derived from Rag-2–/– OT-II transgenic mice (data not shown).
|
|
|
To analyze the fate of the transferred autoreactive T cells, we examined whether the transplanted Dsg3-reactive T cells proliferated in vivo in the recipient Rag-2–/– mice, using several different systems. First, Dsg3-reactive or OVA-specific T cells were labeled with CFSE and transferred into Rag-2–/– mice in combination with primed Dsg3–/– B cells. On the 10th day after adoptive transfer, diluted CFSE was detected in the spleen of mice treated with pathogenic and nonpathogenic Dsg3-reactive T cell lines as well as those receiving irrelevant OVA-specific T cells (Fig. 5A), indicating that the transferred T cells were viable and expanded in vivo irrespective of their antigenic specificity or pathogenic activity. This early and nonspecific T cell proliferation was consistent with homeostatic proliferation (18, 19), which is a proliferative response of mature T cells in the lymphopenic environment to restore the lymphocyte pool size (20). Since it has been reported that the influence of homeostatic proliferation is negligible beyond 30 days of transfer (21), T cell proliferation was evaluated on day 37 by BrdU incorporation in the spleen of recipient mice. BrdU-bearing proliferating CD4+ T cells were frequently detected in mice treated with Dsg3-reactive T cell lines irrespective of their pathogenicity, but not in mice treated with irrelevant OVA-specific T cells (Fig. 5B). The in vivo expansion of the Dsg3-reactive T cells was further evaluated by the expression of Ki-67, a marker for cell proliferation. In recipient mice, Dsg3-reactive and OVA-specific T cells expressed Ki-67 with similar frequencies on day 10, but Ki-67 expression was exclusively detected in the Dsg3-reactive T cells, irrespective of their pathogenicity, on day 37 (Fig. 5C). These findings together indicate that the transferred Dsg3-reactive T cells persistently proliferate in vivo, independent of their pathogenicity. Thus, the in vivo proliferative capacity did not account for the presence or absence of the in vivo pathogenicity of individual T cell lines.
|
Table II summarizes the antigenic Dsg3 fragments, functional TCR Vβ gene usage, and expression profiles of cytokines (IL-2, IL-4, IL-6, IL-10, IL-17, IFN-
, and TGF-β) and chemokine receptors (CCR4, CCR7, CXCR3, CXCR5, and CRTH2) in the 20 Dsg3-reactive T cell lines evaluated for their pathogenicity, which included 13 clones. To identify T cell-derived factors associated with in vivo pathogenicity, the individual characteristics were compared between the 7 T cell lines with in vivo pathogenicity and the 13 lines without it. This analysis showed that all of the pathogenic T cell lines expressed IL-4 and IL-10, and the frequency of lines expressing IL-4 or IL-10 was significantly higher in the pathogenic than in the nonpathogenic group (p = 0.045 for both comparisons). There was no significant difference in the other characteristics between these two groups.
To examine the in vivo homing profiles of the transferred Dsg3-reactive T cell lines, spleen sections were stained with TCRβ for Dsg3-reactive T cells and with CD19 for B cells. Both the Dsg3-reactive T cell lines and the B cells had accumulated in the spleen and formed a lymphoid follicle-like structure. The Dsg3-reactive T cells were mainly detected in the T cell area, but some had infiltrated into the B cell area (Fig. 6A). There was no difference in the number of T cells within the B cell area between mice treated with pathogenic T cell lines and those treated with nonpathogenic T cell lines (Fig. 6B), indicating that the presence or absence of pathogenicity in the Dsg3-reactive T cell lines was not due to a difference in the in vivo homing profiles.
|
We next assessed the roles of IL-4 and IL-10 released by Dsg3-reactive T cells in the mouse PV model, in vitro and in vivo. First, the IgG anti-Dsg3 Abs produced in vitro were measured in the culture supernatants of splenic B cells from rDsg3EHis-immunized Dsg3–/– mice stimulated with soluble recombinant CD40L in the presence of exogenous IL-4, IL-10, or IFN-
. As shown in Fig. 7A, IL-4 significantly promoted the production of IgG anti-Dsg3 Abs from primed Dsg3–/– B cells, but neither IL-10 nor IFN-
had such activity. Next, recombinant adenovirus harboring soluble cytokine receptors (IL-4R
, IL-10R
, or IFN-
R1) was administered to Rag-2–/– mice via the tail vein to neutralize IL-4, IL-10, or IFN-
in vivo. Five days later, the pathogenic Dsg3-reactive T cell clone 147#48 and primed Dsg3–/– B cells were adoptively transferred into immunodeficient mice. The in vivo expression of soluble IL-4R
significantly suppressed the IgG anti-Dsg3 Ab production (Fig. 7B) and the PV skin phenotype (Fig. 7C), but the expression of soluble IL-10R
or soluble IFN-
R1 had no effect. Concordant results were obtained from six independent experiments using clone 147#48, and from four experiments using another pathogenic clone, 164#2.
|
| Discussion |
|---|
|
|
|---|
Our in vivo finding that T cell-derived IL-4 plays a critical role in this mouse model of PV may also be relevant to human PV, because a previous report demonstrated the presence of Dsg3-reactive T cells capable of producing IL-4 in PV patients, but not in healthy controls (22). Since we showed that exogenous IL-4 directly stimulated B cells to produce anti-Dsg3 Abs in vitro, IL-4 produced by Dsg3-reactive T cells is likely to play an essential role in pathogenic anti-Dsg3 autoantibody production. Our results further indicate that IL-4 is essential but not enough to induce PV phenotype, because some of the nonpathogenic Dsg3-reactive T cell lines express IL-4. The pathogenic role of T cell-derived IL-4 has been previously investigated in mouse models for several autoantibody-mediated autoimmune diseases. For example, in experimental autoimmune myasthenia gravis, the disease phenotype is more severe and lasts longer in IL-4–/– mice, indicating a role for IL-4 in preventing the disease (23, 24). In this regard, it has been shown that acetylcholine receptor-reactive T cell clones generated from myasthenia gravis patients fail to secrete IL-4 (25), and that acetylcholine receptor-stimulated IL-4 secretion from PBMC is rarely detected in myasthenia gravis patients (26). Additionally, experimental Graves disease can be induced in IFN-
–/– mice, but not in IL-4–/– mice, indicating a requirement for IL-4 in disease induction (27), while IL-4 was shown to exert an inhibitory effect in another mouse model for Graves disease (28). These inconsistent results suggest that the roles of IL-4 in the pathogenic processes of autoantibody-mediated autoimmune diseases are complex, but they may also reflect the limitation of studies using gene-deficient mice to evaluate the roles of cytokines in autoimmune pathogenesis. Congenital defects in systemic cytokine production are known to affect the physiologic development of the immune system. Moreover, IL-4 secreted by non-T cells could potentially regulate the autoimmune pathogenesis. Our system enables the in vivo effector function of autoreactive T cell clones to be evaluated without the influence of these factors.
It is unclear what determines the nature of Dsg3-reactive T cells in terms of pathogenicity. Our results clearly show that there were a wide variety of gene expression profiles among Dsg3-reacive T cell clones. This heterogeneity is probably generated in a hierarchy during T cell development, and Dsg3-reactive T cells with all of the quantitative and qualitative features required for the PV phenotype induction in our experimental system were regarded as pathogenic clones. Therefore, it is probable that nonpathogenic Dsg3-reactive T cell clones may be able to induce the PV phenotype when missing factors would be supplemented with an appropriate microenvironment. In this regard, it would be interesting to examine if transfer of a large number of the nonpathogenic T cell clone or transfer of the nonpathogenic T cell clone in the presence of exogenous IL-4 would induce the PV phenotype.
Although systemic corticosteroids and other immunosuppressants have been shown to reduce the mortality rate in PV patients, some cases are still refractory to these conventional therapies (29). Recent reports showing remarkable effects of biologics targeting molecules critically involved in the pathogenic process, such as TNF-
and IL-6, have resulted in dramatic changes in the treatment algorithms of several inflammatory diseases, including rheumatoid arthritis and Crohns disease (30, 31, 32). Therefore, anti-IL-4 biologics are a potential therapeutic strategy for refractory PV. In this regard, humanized anti-IL-4 mAb and soluble IL-4R
have already been manufactured for the treatment of allergic diseases, such as asthma, and shown to be well tolerated in clinical trials (33, 34). Further studies are necessary to evaluate the efficacy of anti-IL-4 biologics in patients with severe PV.
| Acknowledgments |
|---|
| Disclosures |
|---|
|
|
|---|
| Footnotes |
|---|
1 This work was supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan, the Health and Labour Sciences Research Grants for Research on Measures for Intractable Diseases from Ministry of Health, Labor and Welfare of Japan, and Keio Gakuji Academic Development Funds. ![]()
2 Address correspondence and reprint requests to Dr. Masataka Kuwana, Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. E-mail address: kuwanam{at}sc.itc.keio.ac.jp ![]()
3 Abbreviations used in this paper: Dsg3, desmoglein 3; PV, pemphigus vulgaris; MalBP, maltose-binding protein. ![]()
Received for publication January 30, 2008. Accepted for publication May 13, 2008.
| References |
|---|
|
|
|---|
- and β-chain genes under the control of heterologous regulatory elements. Immunol. Cell Biol. 76: 34-40. [Medline]This article has been cited by other articles:
![]() |
H. Takahashi, M. Kuwana, and M. Amagai A Single Helper T Cell Clone Is Sufficient to Commit Polyclonal Naive B Cells to Produce Pathogenic IgG in Experimental Pemphigus Vulgaris J. Immunol., February 1, 2009; 182(3): 1740 - 1745. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |