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Institut National de la Santé et de la Recherche Médicale,
*
Unité 503 and
Unité 404, Lyon, France; and
Department of Dermatology, Fukushima Medical University School of Medicine, Fukushima, Japan
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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mRNA expression suggesting local activation of effector cells;
and 2) induction of keratinocyte (KC) apoptosis which gradually
increased to a maximum at the peak of the CHS response. Alternatively,
skin infiltration of CD4+ T cells occurred later and
coincided with the peak of the CHS reaction and the beginning of the
resolution of skin inflammation. Mice deficient in CD8+ T
cells did not develop CHS, whereas mice deficient in CD4+ T
cells developed an enhanced inflammatory response with increased
numbers of CD8+ T cells recruited in the skin associated
with massive KC apoptosis. These data show that CHS is due to the early
and selective recruitment in the skin of CD8+ T cytotoxic 1
effector cells responsible for KC apoptosis. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Although both clinical and experimental studies have suggested roles for CD4+ and CD8+ T cells as the effector T cells mediating CHS (4, 5, 7, 8), studies from this and other laboratories have indicated that: 1) CD8+ Tc1 cells are effector cells in CHS responses in mice (2, 3, 5, 9, 10) and in humans (5, 11); and that 2) CD4+ Th2/Treg cells regulate the magnitude of CHS (2, 3, 5, 12, 13, 14, 15).
The mouse model of CHS to the hapten 2,4-dinitrofluorobenzene (DNFB)
that we have extensively analyzed in recent years shows that CHS is
exclusively mediated by CD8+ Tc1 CTLs, which
develop in secondary lymphoid organs upon hapten presentation by MHC
class I-expressing DC (16, 17). These
CD8+ effector T cells migrate to the challenged
site (9, 12, 18) and initiate the skin inflammation via
Fas and/or perforin-mediated cytolytic function (9).
Indeed, these data suggested that the development of CHS was secondary
to the presentation of haptenated peptides by MHC class I-expressing
skin cells to specific CD8 CTLs. However, little is known about the
precise mechanisms by which the specific T cells enter the skin and are
activated. For initial T cell recruitment, an important role of
complement has been proposed in which C5a acts on mast cells and
platelets, leading to release of mediators such as TNF-
and
serotonin that activate local endothelia to facilitate T cell
recruitment (19, 20, 21). Although we have shown that
CD8+ T cells can rapidly infiltrate the
challenged skin, the recruitment kinetics of CD8+
T cells and of CD4+ T cells into the skin has not
been analyzed. In addition, the nature of the cell type involved in
hapten presentation to specific T cells during the elicitation phase of
CHS remains to be determined. It has been postulated that haptens are
taken up by epidermal DC which migrate to the dermis, where they can
present haptens to specific T cells (22). However, other
studies suggested that DC are not involved in hapten presentation to T
cells during the elicitation phase of CHS, and that keratinocytes (KC)
and other skin resident cells could be the APCs
(23, 24, 25).
In the present study, we show that the development of the skin inflammation during the efferent phase of CHS is initiated by rapid recruitment of CD8+ T cells in the epidermis of challenged skin, associated with the induction of KC apoptosis. CD4+ T cell infiltration occurs hours later at a time where the CHS response starts to lessen. Thus, the CHS reaction is secondary to differential recruitment in the skin of effector Tc1 CD8+ T cells and down-regulatory Th2/Treg CD4+ T cells.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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BALB/c mice (IFFA CREDO, L’Arbresle, France) were used between 6 and 10 wk of age.
Reagents
DNFB (Sigma Aldrich, St. Louis, MO) and picryl chloride (trinitrophenyl (TNP); BDH Laboratory Supplies, Poole, U.K.) were freshly prepared before CHS assays.
Abs used in in vivo experiments comprised anti-CD4 and anti-CD8 mAbs, produced respectively by the hybridoma H 35.17.2, kindly provided by G. Milon (Institut Pasteur, Paris, France), and the hybridoma GK 1.5 purchased from American Type Culture Collection (Manassas, VA). For immunohistochemistry, the following mAbs were used: anti-CD8 (KT-15 rat IgG2a, LE12 9TE, Harlan Sera-Lab, Loughborough, U.K.), anti-CD4 (GK 1.5 rat IgG2b, Leinco Technologies, Ballwin, MO), anti-MHC class II (CD311 rat IgG2b, kindly provided by A. Glasebrook, Lilly Research Laboratories, Indianapolis, IN; Ref. 26), biotinylated rabbit anti-rat IgG (H + L) (Vector Laboratories, Burlingame, CA), biotinylated alkaline phosphatase-streptavidin (StreptABComplex/AP; DAKO, Glostrup, Denmark).
Assay for CHS to DNFB
DNFB was diluted in acetone and olive oil (4/1) immediately before use. The procedure used for the CHS, i.e., the mouse ear swelling test, has been described elsewhere (27). Briefly, 25 µl of 0.5% DNFB solution was applied to a 2-cm2 section of shaved dorsal skin. Five days later, test and control animals received on both sides of the left ear 5 µl of 0.2% DNFB or of an irrelevant hapten, 1% TNP, to test for the hapten specificity of ear swelling. The vehicle (acetone/olive oil) was applied on the right ear. Ear thickness was monitored using a micrometer (J15, Blet, Lyon, France) before challenge and every day after challenge. The ear swelling was calculated as [(T–To) left ear] - [(T–To) right ear], where T and To represent values of ear thickness before and after challenge, respectively.
In each experimental group, some mice were sacrificed at different time intervals after DNFB challenge for histological and PCR analysis.
Ab depletion of CD4+ and CD8+ T cells in vivo
Mice were given i.p. injections of 200 µl 1/10 diluted anti-CD4 or anti-CD8 mAb on days -1, 0, +1, and +4 of skin sensitization. Cell depletion was assessed +1 and +4 day of skin sensitization by staining for CD4 and CD8 molecules on PBMC recovered from retroorbital plexus. In all cases, specific depletion exceeded 95% on both days.
Histology and immunochemistry
Skin samples collected at different times after challenge were either paraffin embedded for histological staining with H&E, or deep frozen in OCT compound (MILES, Torrance, CA) for immunohistochemistry. Frozen sections were cut (6 µm), fixed in acetone for 10 min, and incubated in PBS-5% FCS. The sections were then sequentially incubated with: 1) rat anti-CD4, anti-CD8, or isotype-control mAb; 2) biotinylated rabbit anti-rat IgG (H + L); 3) biotinylated alkaline phosphatase-streptavidin. The labeling was developed using 5-bromo-4-chloro-3-indolyl phosphate/nitroblue tetrazolium as a substrate, and the sections were counterstained with Fast Red.
For analysis of the epidermal sheets, the epidermis from the ears was peeled off the connective tissue by incubation for 90 min at 37°C in PBS supplemented with 20-mM EDTA (Sigma Aldrich). The sheets were incubated overnight at 4°C with the primary anti-mouse MHC class II mAb. Three washes in PBS were followed by the same procedure described above except for counterstain with Fast Red. Some pieces of the epidermis were subjected to TUNEL staining.
TUNEL staining
TUNEL staining was done on paraffin-embedded sections and epidermal sheets using the in situ cell death detection kit AP (Boehringer Mannheim, Mannheim, Germany) following the manufacturer’s instructions. For epidermal sheets, the reaction was developed using 3-amino-9-ethylcarbazole substrate and H2O2 (DAKO).
RNA extraction and RT-PCR analysis of CD8 and IFN- mRNA
At different time points after challenge, ear samples were
collected from sensitized or unsensitized mice and frozen in liquid
nitrogen. The detection of RNA was conducted as described in details
elsewhere (28). Briefly, total RNA was extracted using a
RNAXEL kit (Eurobio, Les Ullis, France). After DNase I treatment, 1
µg of total mRNA was reverse transcribed using poly(dT)15 primers and
Superscript II RT (Life Technologies, Rockville, MD; 90 min 37°C).
The amount of RNA to be used for the detection was normalized using the
housekeeping gene hypoxanthine phosphoribosyltransferase (HPRT) as
reference. The cDNA obtained was amplified using different sets of
primers, for HPRT (5' primer, 5'-GTA ATG ATC AGT CAA CGG GGG AC-3'; 3'
primer, 5'-CCA GCA AGC TTG CAA CCT TAA CCA-3'), for CD8 (5' primer,
5'-AGG ATG CTC TTG GCT CTT CC 3'-3' primer: 5'-TCA CAG GCG AAG TCC AAT
CC-3'), for IFN- (5' primer, 5'-GCT CTG AGA CAA TGA ACG CT-3'; 3'
primer, 5'-AAA GAG ATA ATC TGG CTC TGC-3'), and for CD4 (5' primer,
5'-AGC AAC TCT AAG GTC TCT AAC C-3'; 3' primer, 5'-AGA GTC AGA GTC AGG
TTG CC-3'). The amplifications were conducted with 29 cycles for HPRT
and 33 cycles for IFN-, CD8, and CD4 (1 min at 94°C, 1 min 30
s at 60°C, 2 min at 72°C). The PCR products were analyzed on 1.5%
agarose gel.
Statistical analysis
All experimental groups consisted of five mice, and all experiments were performed at least three times. The statistical significance of differences between mean values of groups was evaluated with the one-way factorial ANOVA (p < 0.05).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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We have previously shown that CHS to DNFB in C57BL/6 (H2-b) mice
was mediated by CD8+ T cells and down-regulated
by CD4+ T cells (3). We confirm here
that the pathophysiology of CHS is similar in BALB/c (H2-d) and C57BL/6
mice. Sensitized BALB/c mice developed a CHS reaction upon challenge
with DNFB which peaked at 24 or 48 h, and faded away from day 3
(Fig. 1
a).
CD4+ T cell-depleted mice developed an enhanced
CHS reaction with a >2-fold increase in skin inflammation 48 h
after challenge, confirming that CD4+ T cells are
necessary for the down-regulation of the CHS response. Conversely, the
CHS response was inhibited in CD8+ T
cell-depleted mice. No ear swelling was observed when DNFB-sensitized
mice were challenged with an irrelevant hapten TNP (data not shown).
Histological analysis of challenged sites showed that CHS in wild-type
animals was associated with vascular enlargement, dermal edema, and
infiltration by mononuclear cells accompanied by a few
polymorphonuclear cells (Fig. 1f). These histological
changes were dramatically enhanced in CD4+ T
cell-depleted mice (Fig. 1g). In addition, a few
eosinophilic, dyskeratotic cells were observed in the epidermis (data
not shown). There were no histological changes in
CD8+ T cell-depleted mice (Fig. 1h).
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CHS reaction is due to early recruitment of CD8+ T cells in challenged skin
Because CHS reaction is mediated by CD8+ T cells and down-regulated by CD4+ T cells, we hypothesized that development of the hapten-specific skin inflammation could be due to the selective and rapid recruitment of CD8+ effector cells in the challenged skin. To test for this hypothesis, the kinetics of CD8+ and CD4+ T cell infiltration in the skin was analyzed by immunohistochemistry and RT-PCR.
Immunohistochemical analysis of ear skin from sensitized but
unchallenged mice revealed a lack of CD8+ cells
(Fig. 2a), whereas some
scattered CD4+ cells could be found in the dermis
(Fig. 2b). In the course of the CHS response,
CD8+ T cells could be detected as early as
12 h after challenge (at a time when no ear swelling was yet
observed; Fig. 2c), while the number of
CD4+ cells remained unchanged (Fig. 2d). CD8+ T cells were found mostly in
the dermis, but a few were also present at the dermal-epidermal
junction. At 24 h postchallenge, corresponding to the peak of the
skin inflammatory response, infiltration of both
CD8+ and CD4+ T cells was
observed (Fig. 2, e and f).
CD8+ T cells primarily infiltrated the
superficial dermis and the epidermis (Fig. 2e). In contrast,
CD4+ T cells were found only in the dermis (Fig. 2f). Interestingly, CD4+ T
cell-depleted mice, which develop an enhanced CHS reaction, exhibited
increased numbers of CD8+ T cells infiltrating
the skin and the epidermis (Fig. 3, a and b), compared with untreated BALB/c mice
(Fig. 3c) at 24 h postchallenge. The average number of
CD8+ T cells in the skin at the peak of the CHS
response (24 h after challenge) was 100 and 170 cells/500 basal
epidermal cells, for untreated and anti-CD4 mAb-treated mice,
respectively (Fig. 3d).
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mRNA during the
course of the CHS reaction to DNFB. Ear samples from previously
sensitized mice were collected at different time points after DNFB
challenge and subjected to mRNA extraction and semiquantitative RT-PCR
analysis using HPRT mRNA as internal standard (Fig. 4, a and b). CD8
and IFN- mRNA were detected neither in skin of naive mice, in
unsensitized challenged mice, nor in sensitized mice before challenge.
During CHS, CD8 and IFN- mRNA were first detected by 6 h after
challenge, confirming that activated, IFN--producing
CD8+ T cells infiltrate the challenged skin.
CD8+ mRNA increased gradually up to 48 h,
whereas IFN- mRNA expression peaked at 24 h and decreased
thereafter (Fig. 4). CD4 mRNA was present at low levels in normal skin
(compatible with the rare CD4+ cells found in the
dermis of normal skin; Fig. 2
b), remained stable up to
24 h postchallenge, but markedly increased thereafter (Fig. 4).
These data confirmed and extended the results of immunohistological
analysis and showed that early recruitment of the challenged skin by
CD8+ T cells during CHS precedes
CD4+ T cell infiltration.
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We have previously shown that cytotoxicity through the Fas or the
perforin pathway is mandatory for CD8+ T
cell-mediated CHS and associated with the development of
hapten-specific, MHC class I-restricted CD8+ T
cells (9). Thus, we examined whether
CD8+ T cell recruitment in the skin at the sites
of challenge is coincidental with localization of apoptosis of skin
cells. We studied the kinetics of apoptosis in the skin during the
course of CHS using the TUNEL-labeling method. Apoptotic cells were
found neither in the ear skin of normal BALB/c mice (data not shown),
nor in that of unsensitized challenged mice (Fig. 5a). In sensitized challenged
mice, TUNEL+ apoptotic cells were observed mostly
in the epidermis, as early as 6 h postchallenge, a time
corresponding to the onset of the skin infiltration by
CD8+ T cells (Fig. 5b). The maximum
number of apoptotic cells was observed at 24 h and involved mostly
epidermal cells, although scattered TUNEL+ cells
were found in the dermis (Fig. 5c). Interestingly, the
number of apoptotic cells was dramatically increased in mice treated
with anti-CD4 mAb, where, in some areas, almost all basal KC
appeared TUNEL+ within 24 h postchallenge
(Fig. 5f). In both untreated and anti-CD4-treated mice,
apoptotic KC developed with comparable kinetics, being first detected
as early as 6 h postchallenge, and reaching maximal numbers at
24 h (Fig. 5d).
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). Before challenge, the epidermis
contained a network of class II+ LC (Fig. 6a), but was devoid of apoptotic cells (Fig. 6c).
Alternatively, at 24 h postchallenge, very few LC remained in the
epidermis (Fig. 6b; consistent with previous studies which
have demonstrated that epicutaneous application of haptens induces LC
emigration from the epidermis; Ref. 29), whereas high
numbers of apoptotic epidermal cells were found (Fig. 6d).
Thus, an inverse correlation between the number of LC and the number of
apoptotic cells was found (Fig. 6e). Double staining for
class II and TUNEL+ cells confirmed lack of class
II+ TUNEL+ apoptotic LC
(Fig. 6f). These data demonstrate that KC, but not LC, are
the main targets of CD8+ CTLs during the
elicitation of CHS.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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mRNA whose production in our model is restricted to
CD8+ T cells (9, 30, 31, 32); 3)
apoptosis of KC coincided with the appearance of
CD8+ T cells in the skin and gradually increased
proportionally to the number of CD8+ T cells
infiltrating the skin. In contrast to CD8+ T cells, CD4+ T cells are not recruited in the first hours following challenge. They first appeared in the challenged site at 24 h only, and their recruitment was associated with a decrease in the inflammatory reaction and a diminution of apoptotic cells in the epidermis. Thus, it is tempting to speculate that the differential kinetics in the recruitment of CD8+ T cells and CD4+ T cells are responsible for the typical skin inflammation of CHS. The CHS reaction can be defined as an acute Ag-specific inflammation which develops as the result of the recruitment of CD8+ T cells in the absence of CD4+ down-regulatory T cells. CHS decreases and resolves as soon as CD4+ T cells infiltrate the inflamed skin. CD4+ T cells being responsible for the down-regulation of CHS is supported by the observation that CD4+ T cell-deficient mice develop an enhanced CHS reaction with a markedly increased and sustained infiltration of CD8+ T cells in the skin associated with an increase in the number of apoptotic KC.
Recruitment of lymphocytes into inflamed skin is a multistep process
involving recognition of vascular endothelial cells and extravasation.
Haptens are able to rapidly induce expression of E- and P-selectins,
VCAM-1 and ICAM-1 on endothelial cells (33, 34, 35, 36). Several
reports have shown that 
2 h after topical application of Ag to the
ear of sensitized mice, there is marked edema due to local release of
TNF-, serotonin, and histamine from mast cell and platelets
(19, 37, 38, 39, 40, 41), in which complement C5 might play an
important role (20, 21). Early release of TNF- induced
expression of VCAM-1 and ICAM-1 on the luminal surface of local
endothelium (36). These adhesion molecules mediate
rolling, adhesion, and extravasation of blood leukocytes expressing
cutaneous lymphocyte-associated Ag or P-selectin ligands into the skin.
Chemokines regulate the lymphocyte traffic in part by triggering arrest
of lymphocytes rolling on the endothelium (42). Among the
large variety of chemokines able to attract T cells in inflamed
tissues, CCL2 (monocyte chemotactic protein-1 (MCP-1), CCR2
ligand) appears pivotal for the recruitment of effector T cells in the
skin during the CHS reaction (43, 44, 45). Production of MCP-1
by KC and skin cells (34, 46) occurs 4–6 h after hapten
challenge, clearly before skin infiltration with T cells
(34). Moreover, MCP-1 has been shown to augment
lymphocyte cytotoxicity, and therefore, could be involved in both
recruitment and optimal activation of hapten-specific effector CTLs in
the skin (47).
The reason for the sequential infiltration of the skin by
CD8+ first and then by CD4+
T cells is unclear. Two hypotheses may explain this observation.
Activation and expansion of hapten-specific CD8+
Tc1 effector cells in lymphoid organs may precede that of regulatory
Th2/Treg CD4+ T cells (5, 31).
Indeed, in vivo priming of specific CD8+ T cells
is achieved within 5 days, does not require help from
CD4+ T cells (3), and is independent
of the CD40 ligand engagement (48). Alternatively,
differential expression of homing receptors and sequential expression
of chemokines in the skin may account for selective attraction of Tc1
CD8+ effector cells, preceding that of regulatory
Th2/Treg CD4+ T cells. In this respect,
functional ligands for E- and P-selectins (cutaneous
lymphocyte-associated Ags, P-selectin glycoprotein ligand-1) appear to
be more highly expressed on Th1 cells than on Th2 cells
(49), in keeping with the enhanced ability of Th1 cells to
enter delayed type hypersensitivity sites, compared with Th2 cells
(50). Recent studies showed that IL-12, which is mandatory
for priming of Th1/Tc1 cells, is required for the expression of
P-selectin ligands on both CD4+ and
CD8+ T cells, which are able to enter inflamed
tissues (51). Alternatively, Th2/T cytotoxic 2 cells
primed by Ag in the presence of IL-4 and anti-IFN- Ab are unable
to bind to P-selectin (51).
It may be postulated that CD8+ T cell activation
in the skin (resulting in IFN- production, cytotoxicity, and
possibly chemokine production) provides the signals required for
recruitment of CD4+ T cells. Indeed, our results
show that recruitment of CD4+ T cells occurs
several hours after that of IFN--producing
CD8+ T cells and beginning of KC apoptosis. In
several models, initial Th1 cell infiltration was followed by massive
recruitment of Th2 cells (52, 53). It has been proposed
that secretion of Th2 cell-attracting chemokines, such as CCL1 (I-309,
CCR8 ligand) by activated Th1 cells (54) or CCL22
(macrophage-derived chemokine (MDC), CCR4 ligand) by skin cells during
CHS (55) might serve to recruit CCR4/CCR8-expressing Th2
cells for down-regulating Th1-mediated inflammatory responses
(56). Recent studies in humans have reported that I-309
attracted more efficiently hapten-specific regulatory
CD4+ T cells (Treg and Th2) than Th1 cell clones
(57), consistent with the observation that CCR8 is
expressed on Th2/Treg, but not on Th1 cells (58). In
addition, MDC-injection in the skin allowed preferential recruitment of
CCR4-expressing Th2 cells (59).
Our data showing apoptosis of KC and not of LC after hapten challenge in sensitized animals suggest that KC are the main APCs able to activate DNFB-specific CD8+ T cells. Although LC are undoubtedly involved in Ag presentation during the sensitization phase of CHS, its role during the elicitation phase is unclear. The fact that LC migrate away from the site of Ag application is an argument against their active participation in T cell activation. In this respect, a model of LC-depleted mice using topical steroid application showed markedly enhanced CHS responses, suggesting that LC are not the relevant APC for activation of effector cells during the elicitation phase, but may rather provide down-regulatory signals (23). However, it cannot be ruled out that LC might be involved in hapten presentation to the early-arriving CD8 CHS effector T cells before they depart for the lymphoid organs.
In summary, the results presented here support the following model for
recruitment of CD8+ effector Tc1 cells and
CD4+ Th2/Treg cells in the skin during CHS: 1)
haptens initiate CHS by inducing a release of local endothelium
activators and also the rapid production of MCP-1 by skin cells able to
recruit CCR2+ Tc1 cells; 2) hapten-specific
effector Tc1 cells activated in the skin produce IFN- and induce KC
cytotoxicity; 3) this process induces the synthesis of inflammatory
cytokines and chemokines responsible for massive infiltration of
mononuclear and polymorphonuclear cells and development of skin
inflammation; 4) among the chemokines produced, I-309 and MDC may
recruit CCR4 and CCR8-expressing Th2/Treg cells which may down-regulate
the cutaneous inflammation by production of IL-10 and IL-4
immunoregulatory cytokines (5, 60).
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Hitoshi Akiba, Department of Dermatology, Fukushima Medical University School of Medicine, Hikarigaoka-1, Fukushima, 960-1295, Japan. E-mail address: hakiba{at}fmu.ac.jp
3 Current address: WSH 2881.229, Novartis Pharma, CH-4002 Basel, Switzerland. E-mail address: jeanne.kehren{at}pharma.novartis.com
4 Abbreviations used in this paper: CHS, contact hypersensitivity; Tc1, T cytotoxic 1; Treg, T regulatory; DNFB, 2,4-dinitrofluorobenzene; DC, dendritic cell; TNP, trinitrophenyl; LC, Langerhans cell; KC, keratinocyte; MCP-1, monocyte chemotactic ptotein-1; MDC, macrophage-derived chemokine; HPRT, hypoxanthine phosphoribosyltransferase.
Received for publication October 23, 2001. Accepted for publication January 7, 2002.
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 B. Dubois, L. Chapat, A. Goubier, M. Papiernik, J.-F. Nicolas, and D. Kaiserlian Innate CD4+CD25+ regulatory T cells are required for oral tolerance and inhibition of CD8+ T cells mediating skin inflammation Blood, November 1, 2003; 102(9): 3295 - 3301. [Abstract] [Full Text] [PDF]
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P. Saint-Mezard, C. Chavagnac, S. Bosset, M. Ionescu, E. Peyron, D. Kaiserlian, J.-F. Nicolas, and F. Berard Psychological Stress Exerts an Adjuvant Effect on Skin Dendritic Cell Functions In Vivo J. Immunol., October 15, 2003; 171(8): 4073 - 4080. [Abstract] [Full Text] [PDF]
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), or treated with anti-CD4 (
) or
anti-CD8(•) mAb. Unsensitized challenged mice exhibited no ear
swelling (
). Results are expressed as the mean ear swelling ±
SD at different time points after challenge, and are representative of
three independent experiments. The letter p (p <
0.05) indicates statistical significance compared with untreated mice.
b–h, Histological analysis of CHS reaction.
Four-micrometer thick sections of ears recovered from either untreated
(c and f), CD4+ T
cell-depleted (d and g), or
CD8+ T cell-depleted (e and
h) mice at 6 h (c–e) and 24 h
(f–h) after challenge were stained with H&E. At 6
h after challenge, skin sections from untreated (c),
CD4+ T cell-depleted (d), and
CD8+ T cell-depleted (e) mice exhibited
normal histological features similar to that of naive mice
(b). At 24 h after challenge, sections from
untreated mice (f) displayed the characteristic features
of the CHS reaction including dermal edema, mononuclear cell
infiltration, and vascular enlargement, which did not appear in
CD8+ T cell-depleted mice (h). Sections from
CD4+ T cell-depleted mice (g) exhibited
exaggerated inflammatory reaction, including enhanced edema,
vasodilatation, and massive mononuclear cell infiltration.
Magnification: b–h, x200.
), CD4 (
), and IFN-
