IL-1 alpha, but not IL-1 beta, is required for contact-allergen-specific T cell activation during the sensitization phase in contact hypersensitivity.

Contact hypersensitivity (CHS) is a T cell-mediated cellular immune response caused by epicutaneous exposure to contact allergens. In this reaction, after the first epicutaneous allergen sensitization, Langerhans cells (LC) catch allergens and migrate from the skin to draining lymph nodes (LN) and activate naive T cells. Although IL-1 is suggested to be involved in these processes, the mechanisms have not been elucidated completely. In this report, to elucidate roles of IL-1alpha and IL-1beta in CHS, we analyzed ear swelling in 2,4,6-trinitrochlorobenzene (TNCB)-induced CHS using gene-targeted mice. We found that ear swelling was suppressed in IL-1alpha-deficient (IL-1alpha(-/-)) mice but not in IL-1beta(-/-) mice. LC migration from the skin into LN was delayed in both IL-1alpha(-/-) and IL-1beta(-/-) mice, suggesting that this defect was not the direct cause for the reduced CHS in these mice. However, we found that the proliferative response of trinitrophenyl (TNP)-specific T cells after sensitization with TNCB was specifically reduced in IL-1alpha(-/-) mice. Furthermore, adoptive transfer of TNP-conjugated IL-1-deficient epidermal cells (EC) into wild-type mice indicated that only IL-1alpha, but not IL-1beta, produced by antigen-presenting cells in EC could prime allergen-specific T cells. These observations indicate that IL-1alpha, but not IL-1beta, plays a crucial role in TNCB-induced CHS by sensitizing TNP-specific T cells.     

GATA-3 regulates contact hyperresponsiveness in a murine model of allergic dermatitis

Contact hypersensitivity (CHS) is thought to be associated mainly with the activation of T helper (Th) type 1 cells. However, evidence also suggests that Th type 2 cells (Th2) and cytokines play roles in the development of CHS in humans. The present study examines the Th2 response during the development of CHS in response to 2,4,6-trinitrochlorobenzene (TNCB) in GATA-3-transgenic (GATA-3 Tg) mice. GATA-3 Tg mice were immunized with 7% TNCB applied to abdominal shaved skin. Seven days later, the mice were challenged with 1% TNCB applied to the left ear. Ear swelling, cytokine production in the skin of the ear, and the levels of IgE, IgG1 and IgG2a were measured. Furthermore, we examined the effects of medical treatment on TNCB-induced contact dermatitis using this model. The ear-swelling responses of TNCB-sensitized/challenged GATA-3 Tg mice were significantly greater than those of similarly treated wild-type (WT) mice. The expression of both IL-5 and IL-13 in TNCB sensitized/challenged skin tissues and the IgE response after challenge were obviously increased in the GATA-3 Tg mice, whereas the expression of IFN-γ was identical in the challenged skin tissues of GATA-3-Tg and WT mice. When TNCB-sensitized GATA-3 Tg mice were treated with a high dose of tacrolimus, ear swelling was not significantly decreased, compared with the results in WT mice. These results suggest that GATA-3-induced Th2-dominant responses play a critical role in the pathogenesis of allergic types of dermatitis, such as atopic dermatitis, and may lead to useful new drug development in the future.     

Sema4D is required in both the adaptive and innate immune responses of contact hypersensitivity

Originally recognized as a regulator of axon guidance in the nervous system, Semaphorin 4D (Sema4D, CD100) also participates in various immune responses and many immune-related diseases. However, whether Sema4D is involved in the pathogenesis of contact hypersensitivity (CHS) remains unclear. In this study, we explored the role of Sema4D in oxazolone-induced CHS using Sema4D knockout (KO) mice. We found that Sema4D KO mice developed attenuated CHS responses, as indicated by milder ear-swelling, lower expression of IL-1β, IL-6, CXCL2 and CXCL5, and decreased recruitment of neutrophils, CD8⁺ T cells and CD4⁺ T cells. CHS was impaired in the wide type (WT) mice reconstituted with bone marrow from Sema4D KO mice, indicating that deletion of Sema4D gene in hematopoietic cells played a key role in the alleviated CHS in Sema4D KO mice. CHS was also attenuated in the WT mice transferred with draining lymph nodes (dLNs) cells from oxazolone-sensitized Sema4D KO mice, and the activation and differentiation of hapten-specific CD8⁺ T cells were impaired in Sema4D KO mice. Furthermore, Sema4D KO mice expressed less IL-1β and CXCL2 than WT mice after oxazolone sensitization, and after transferred with dLNs cells from oxazolone-sensitized WT mice, naïve Sema4D KO mice showed attenuated CHS responses upon oxazolone challenge, indicating that the innate immune response of CHS in Sema4D KO mice was also abrogated. Taken together, our findings revealed for the first time that Sema4D positively regulated both the adaptive and innate immune responses in CHS.     

Cytip regulates dendritic-cell function in contact hypersensitivity

Cytohesin-interacting protein (Cytip) is induced during dendritic cell (DC) maturation and in T cells upon activation. It has also been shown to be involved in the regulation of immune responses. Here, we evaluated the functional consequences of Cytip deficiency in DCs using Cytip knockout (KO) mice. No difference in DC subpopulations in the skin draining lymph nodes (LNs) was found between Cytip KO mice and their wild-type counterparts, excluding a role in DC development. To investigate the function of Cytip in DCs in vivo, we used 2,4,6-trinitrochlorobenzene (TNCB)-induced contact hypersensitivity (CHS) as a model system. In the sensitization as well as in the elicitation phase, DCs derived from Cytip KO mice induced an increased inflammatory reaction indicated by more pronounced ear swelling. Furthermore, IL-12 production was increased in Cytip KO bone marrow-derived DCs (BMDCs) after CpG stimulation. Additionally, Cytip-deficient DCs loaded with ovalbumin induced stronger proliferation of antigen-specific CD4(+) and CD8(+) T cells in vitro. Finally, migration of skin DCs was not altered after TNCB application due to Cytip deficiency. Taken together, these data suggest a suppressive function for Cytip in mouse DCs in limiting immune responses.     

Tissue regeneration using macrophage migration inhibitory factor-impregnated gelatin microbeads in cutaneous wounds

Migration inhibitory factor (MIF) responds to tissue damage and regulates inflammatory and immunological processes. To elucidate the function of MIF in cutaneous wound healing, we analyzed MIF knockout (KO) mice. After the excision of wounds from the dorsal skin of MIF KO and wild-type (WT) mice, healing was significantly delayed in MIF KO mice compared to WT mice. Lipopolysaccharide treatment significantly increased [(3)H]thymidine uptake in WT mouse fibroblasts compared to MIF KO mouse fibroblasts. Furthermore, there was a significant reduction in fibroblast and keratinocyte migration observed in MIF KO mice after 1-oleoyl-2-lysophosphatidic acid treatment. We subsequently examined whether MIF-impregnated gelatin slow-release microbeads could accelerate skin wound healing. Injection of more than 1.5 microg/500 microl of MIF-impregnated gelatin microbeads around a wound edge accelerated wound healing compared to a single MIF injection without the use of microbeads. MIF-impregnated gelatin microbeads also accelerated skin wound healing in C57BL/6 mice and diabetic db/db mice. Furthermore, incorporating MIF-impregnated gelatin microbeads into an artificial dermis implanted into MIF KO mice accelerated procollagen production and capillary formation. These findings suggest that MIF is crucial in accelerating cutaneous wound healing and that MIF-impregnated gelatin microbeads represent a promising treatment to facilitate skin wound healing.     

IL-18 is a key proximal mediator of contact hypersensitivity and allergen-induced Langerhans cell migration in murine epidermis

Langerhans cells (LC) migrate rapidly from epidermis to lymph node following epicutaneous application of antigen. In this study, we have explored the role of IL-18, a cytokine with structural similarities to IL-1 beta, in murine LC migration and contact hypersensitivity (CHS), which to oxazolone (OX) and 2-4,dinitrofluorobenzene (DNFB) was suppressed significantly in IL-18 knockout (IL-18-/-) mice and could be rescued by local intradermal administration of IL-18 prior to sensitization, suggesting that the defect in these mice was in the afferent phase of CHS. To determine the effect of IL-18 on LC migration, mice were treated topically with OX or DNFB, and remaining LC numbers were assessed. A significant decline in remaining epidermal LC occurred in wild-type (WT) mice but did not occur in IL-18-/- mice. Sodium lauryl sulfate, a nonantigenic LC migratory stimulus, induced equivalent LC migration in IL-18-/- and WT mice. In IL-18-/- mice, IL-1 beta and TNF-alpha were equally able to mobilize LC from epidermis, indicating that migration in response to these cytokines is not dependent on IL-18 and suggesting that IL-18 acts upstream of these cytokines in the initiation of antigen-induced LC migration. Moreover, IL-1 beta but not IL-18 was able to rescue the defective CHS response observed in caspase-1-/- mice, which have no functional IL-1 beta or IL-18. These data indicate that IL-18 is a key proximal mediator of LC migration and CHS, acting upstream of IL-1 beta and TNF-alpha, and may play a central role in regulation of cutaneous immune responses.     

Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 regulates the induction of Langerhans cell maturation

Recently, we reported that Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 (SHPS-1) plays an important role in the migration of Langerhans cells (LC). Here, we show that SHPS-1 is involved in the maturation of LC. Immunofluorescence analysis on epidermal sheets for I-A or CD86 revealed that LC maturation induced by 2,4-dinitro-1-fluorobenzene (DNFB) or by TNF-alpha was inhibited by pretreatment with an anti-SHPS-1 monoclonal antibody (mAb) or with CD47-Fc fusion protein, a ligand for SHPS-1. Further, FACS analysis demonstrated that I-A(+) LC that had emigrated from skin explants expressed CD80 or CD86, whereas CD47-Fc protein reduced CD80(high+) or CD86(high+) cells. CD47-Fc protein also reduced the up-regulation of surface CD80 or CD86 by LC remaining in the skin explants. In SHPS-1 mutant mice, we observed that the up-regulation of surface CD86 and CCR7 by LC induced by DNFB as well as that of surface CD80 and CD86 by LC in skin explants was attenuated. Finally, contact hypersensitivity (CHS) response was suppressed in SHPS-1 mutant mice and in wild-type mice treated with an anti-SHPS-1 mAb. These observations indicate that SHPS-1 plays an important role in the maturation of LC ex vivo and in vivo, and that SHPS-1-CD47 interaction may negatively regulate CHS.     

Th2 cytokines,IgE and mast cells play a crucial role in the induction of para-phenylenediamine-induced contact hypersensitivity in mice

We previously reported the establishment of a mouse model system of contact hypersensitivity (CHS) to paraphenylemediamine (PPD). In order to analyse the functional contribution of Th2 cytokines, IL-4 and IL-5, in PPD induced CHS, STAT6 deficient (STAT6-/-) and wild-type control (WT) mice (C57BL/6) were immunized by the topical application of a PPD solution, and then the subsequent skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6-/- mice as compared with that of WT mice. A histological analysis showed the infiltration of both eosinophils and neutrophils in the skin of STAT6-/- mice challenged 24 h previously to significantly decrease in comparison with that in the WT mice. The expression of Th2 cytokines (IL-4, IL-5) by ELISA in the PPD-challenged skin tissue specimens as well as the IgE and IgG1 response after challenge were also profoundly reduced in the STAT6-/- mice. The adoptive transfer of the serum obtained from sensitized WT mice for the putative IgE transfer induced a peak response at 3 h and 24 h after challenge. To further investigate the role of mast cells in the induction of PPD-CHS, mast cell deficient W/Wv mice were sensitized with PPD and then were challenged. Maximal ear swelling was detected from 12 to 24 h and another small peak response was observed at 1 h in+/+mice, whereas only a small peak response at 24 h was detected in W/Wv mice. These data indicate that not only Th2 cytokines and IgE but also mast cells play an essential role in the induction of PPD-CHS.     

Diminished Contact Hypersensitivity Response in IL-4 Deficient Mice at a Late Phase of the Elicitation Reaction

Contact hypersensitivity (CHS) is thought to depend on the activation of T cells of Th1 and/or Tc1 type. The role of Th2/Tc2 cells in the contact allergic reaction is not clear. The aim of this study was to analyse the functional contribution of Th2/Tc2 cells in CHS using the interleukin-4 (IL-4) deficient mouse model. Interleukin-4 deficient (IL4T) and control (wt) mice were sensitized by epicutaneous application of 2,4-dinitrofluorobenzene. The ear swelling response measured 24 h after challenge was similar in IL4T and control mice. However, from 48 h onwards, ear swelling values were significantly reduced in IL4T mice. The stimulatory capacity of freshly isolated as well as 3-day cultured epidermal cells, prepared from IL4T and wt mice, for allogeneic T cells in a primary and secondary response, was comparable. The reduced number of T cell receptor (TCR) γδ⁺ cells observed in epidermal sheets prepared from IL4T mice was not responsible for the decreased ear swelling response in IL4T mice, because the use of TCR δ deficient mice lacking TCR γδ⁺ cells revealed a down-regulatory role of this cell population in the CHS response. The data indicate that the effector stage of the CHS response can be subdivided into two phases. The first phase proceeds efficiently in IL-4 deficient mice indicating the dependence on Th1/Tc1 cells, while the second phase does not develop in mice lacking IL-4, suggesting the possibility that Th2/Tc2 cells intensify the reaction.     

Pivotal roles of the parasite PGD2 synthase and of the host D prostanoid receptor 1 in schistosome immune evasion

Prostaglandins (PG) are important modulators of immune and inflammatory responses. We recently demonstrated that the production of PGD(2) by the helminthic parasite Schistosoma mansoni inhibits the migration of epidermal Langerhans cells (LC) to the draining lymph nodes (DLN). Here, we identify the responsible parasite enzyme as being a 28-kDa glutathione-S-transferase (termed Sm28GST). Intradermal injection of Sm28GST in wild-type (WT), but not in D prostanoid receptor (DP) 1-deficient mice abrogates the departure of LC from the epidermis after TNF-alpha or FITC treatment. During infection, DP1 deficiency restores LC migration, but does not enhance the rate of T cell proliferation in the skin DLN. However, relative to WT mice, DLN cells from DP1-deficient infected mice produce dramatically less IFN-gamma and IL-10, but equal amount of IL-4. Interestingly, infected DP1-deficient mice develop a more Th2-biased humoral immune response, a significantly reduced parasitemia and a decreased egg-induced inflammatory response in the liver and intestines. Taken together, we propose that DP1 activation by the Sm28GST-derived PGD(2) could represent a strategy for the schistosome to evade host immune defenses. We also suggest that DP1 is important in the Th1/Th2 balance of the immune response and in inflammatory reactions during infection.     

Protein kinase C transduces the signal for Langerhans' cell migration from the epidermis.

Langerhans' cells (LC) take up antigen in the epidermis and then migrate to the local lymph nodes where they present the antigen to T lymphocytes, initiating cutaneous immune responses. However the intracellular mechanisms which mediate LC migration from the epidermis are unknown. We have demonstrated that activation of protein kinase C (PKC) induces this LC migration. An analogue of diacylglycerol (DAG), the physiological activator of PKC, L-alpha-dioctanoyl glycerol (oDAG), applied topically onto the skin of mice caused a significant depletion in the density of Ia+ and J11d+ epidermal LC. oDAG decreased the density of LC in both BALB/c and C57BL mice 24 hr following application, over a dose range of 0.5-24 microM; 200 or 0.05 microM being ineffective. LC density remained depressed for up to 7 days and oDAG increased the number of fluorescein isothiocyanate (FITC) positive cells in the local lymph nodes of mice treated topically with FITC, indicating that oDAG induced LC migration from the epidermis. Additionally, LC migration from the epidermis induced by the contact sensitizer 2,4,6-trinitrochlorobenzene (TNCB) was blocked when PKC was inhibited by palmitoyl-DL-carnitine chloride (PCC) or D-Sphingosine (Sph), indicating that LC cannot migrate from the epidermis when PKC is inhibited. However, PCC did not inhibit the induction of contact sensitivity. Thus PKC transduces the signal which leads to LC migration from the epidermis, and disruptions in this secondary messenger may interfere with the induction of immune responses in the skin by disturbing LC migration from the epidermis to the local lymph nodes.     

Diversion of CD4+ T cell development from regulatory T helper to effector T helper cells alters the contact hypersensitivity response

Cutaneous sensitization to reactive haptens and subsequent challenge results in a T cell-mediated response, contact hypersensitivity (CHS). Recent results from this laboratory have indicated that hapten sensitization induces two populations of reactive T cells: CD8⁺ T cells producing interferon (IFN)-γ which mediate the response and CD4⁺ T cells producing interleukin (IL)-4 and IL-10 which negatively regulate the magnitude and duration of the response. Since CD4⁺ T cell development to either IFN-γ- (Th1) or IL-4/IL-10- (Th2)-producing cells is dependent upon the cytokine environment during antigen priming, we hypothesized that CD4⁺ T cell induction in a Th1-promoting environment would not only alter the CD4⁺ T cell cytokine-producing phenotype but also the course of the CHS response. Administration of the Th1-promoting cytokine IL-12 during hapten sensitization resulted in a CHS response of greater magnitude following challenge and extended the duration of the response. In hapten-sensitized mice depleted of CD8⁺ T cells, treatment with IL-12 induced effector CD4⁺ T cells. Histological examination of challenged ear tissue from these mice indicated minimal edema and an acute mononuclear cell infiltration more typical of classical delayed-type hypersensitivity than CHS. Hapten-primed CD4⁺ T cells from IL-12 treated, sensitized mice produced IFN-γ, but not IL-4 in response to T cell receptor-mediated stimulation. Use of neutralizing anti-IFN-γ antibody indicated that IL-12 not only directly promoted Th1 development but also indirectly inhibited Th2 development through stimulation of IFN-γ production at the time of hapten sensitization. Overall, these results demonstrate that diversion of CD4⁺ T cell development to Th1 effector cells rather than to Th2 cells alters the efferent nature of CHS and removes a primary regulatory mechanism of the immune response.     

B cells are not required for T cell priming in low zone tolerance to contact allergens and contact hypersensitivity

Low zone tolerance (LZT) to contact allergens is induced by epicutaneous exposure to haptens in subsensitizing doses resulting in an inhibition of contact hypersensitivity (CHS), which, in contrast, occurs after sensitization with immunogenic doses of allergens. Performing the protocol of tolerance induction resulted in robust LZT to allergens in B cell-deficient mice in vivo, indicating that B cells are not required for the induction and effector phase of LZT. However, CHS reactions in vivo were restricted in B cell-deficient mice as compared to wild-type (WT) mice. In contrast, analysis of hapten-specific T cell activation in vitro revealed a strong proliferative response of T cells derived from both WT and B cell-deficient sensitized mice. Similar to WT animals, T cells obtained from tolerized B cell-deficient mice produced a Tc2 cytokine pattern of LZT with high levels of IL-4 and IL-10, whereas sensitization of B cell-deficient mice resulted in the typical Tc1 cytokine profile of CHS. Adoptive transfer of CD8+ effector T cells from tolerized or sensitized B cell-deficient mice induced significant LZT or CHS reactions, respectively, in WT recipients, demonstrating that the development of hapten-specific effector CD8+ T cells of LZT and CHS is independent of B cells.     

Gammadelta T cells assist alphabeta T cells in the adoptive transfer of contact hypersensitivity to para-phenylenediamine

Para-phenylenediamine (PPD) is known to be a common sensitizer of allergic contact dermatitis and contact urticaria. To clarify the mechanism of contact hypersensitivity (CHS) to PPD, we established a mouse model of PPD-induced CHS. BALB/c mice were immunized for 3 consecutive days by painting topically a 2.5% PPD solution on their shaved abdominal skin. On days 5, 7 or 9 after the initial application, the mice were challenged by applications of a 2.5% PPD solution. Maximal ear swelling was determined at 24 h but another statistically significant and smaller ear swelling was observed 1 h after challenge with PPD in a hapten-specific manner. Adoptive cell transfer experiments demonstrated that the ear swelling of the adoptive cell transferred mice displayed an early response at 6 h and a late response from 12 h to 24 h when the recipient mice were challenged immediately after transfer. Both MoAbs and complement treatment of the transferred cells demonstrated that the phenotype of the early response cells which elicited a response at 6 h after challenge was Thy1(+), B220(+), alphabeta TCR(-), gammadelta TCR(-), CD3(-), CD4(-), CD5(+) and CD8(-). The in vitro treatment of effector cells with MoAbs against not only alphabeta TCR but also gammadelta TCR, together with complement, was found to diminish substantially the late response, elicited 12-24 h after challenge. Gammadelta T cells reconstituted the ability of alphabeta T cells to transfer 24 h CHS responsiveness. The phenotype of the gammadelta T cells that assist CHS effector alphabeta T cells was CD3(+), CD4(-) and CD8(+) and these regulatory gammadelta T cells were neither Ag-specific nor MHC-restricted. Furthermore, gammadelta T cells from normal spleen could also assist alphabeta T cells in adoptive transfer of the 24 h CHS response in a non-MHC-restricted manner. RT-PCR demonstrated that alphabeta T cells strongly expressed mRNA IFN-gamma, whereas gammadelta T cells expressed not only IFN-gamma but also IL-4 and IL-10. These data indicate that not only early response cells and alphabeta T cells but also Th2 type gammadelta T cells may play an important role in the elicitation of CHS to PPD.     

Suppressive and pro‐inflammatory roles for IL‐4 in the pathogenesis of experimental drug‐induced liver injury

The pathogenesis of immune‐mediated drug‐induced liver injury (DILI) following halogenated anesthetics, carbamazepine or alcohol has not been fully elucidated. Detecting cytochrome P450 2E1 (CYP2E1) IgG4 auto‐antibodies in anesthetic DILI patients suggests a role for IL‐4 in this hapten‐mediated process. We investigated IL‐4‐mediated mechanisms using our model of experimental DILI induced by immunizing BALB/c (WT) and IL‐4^?/? (KO) mice with S100 liver proteins covalently modified by a trifluoroacetyl chloride (TFA) hapten formed following halogenated anesthetic metabolism by CYP2E1. WT mice developed more hepatitis, TFA and S100 antibodies (p<0.01), as well as T‐cell proliferation to CYP2E1 and TFA (p<0.01) than KO mice. Additionally, WT CD4⁺ T cells adoptively transferred hepatitis to naïve Rag^?/? mice (p<0.01). Pro‐inflammatory cytokines were expectedly decreased in TFA hapten‐stimulated KO splenocyte supernatants (p<0.001); however, IL‐2 and IFN‐γ (p<0.05), as well as IL‐6 and IL‐10 (p<0.001) levels were elevated in CYP2E1‐stimulated KO splenocyte supernatants, suggesting dual IL‐4‐mediated pro‐inflammatory and regulatory responses. Anti‐IL‐10 administered to KO mice increased hepatitis, TFA and CYP2E1 antibodies in KO mice confirming a critical role for IL‐4. This is the first demonstration of dual roles for IL‐4 in the pathogenesis of immune‐mediated DILI by suppressing auto‐antigen‐induced regulatory responses while promoting hapten‐induced pro‐inflammatory responses.     

Quinacrine inhibits the epidermal dendritic cell migration initiating T cell-mediated skin inflammation

Quinacrine (QC) is an anti-inflammatory drug that has been used for the treatment of malaria and rheumatoid diseases. The mechanism(s) underlying the anti-inflammatory activity of QC remains poorly understood. We recently reported the QC-mediated inhibition of the NF-kappaB pathway using an in vitro model. To test this potential mechanism in vivo, we used the contact hypersensitivity response (CHS) to chemical allergen sensitization and challenge in mice as a model of skin inflammation. The results indicated that QC treatment inhibited NF-kappaB activation in the skin during allergen sensitization. This inhibition was reflected by decreased mRNA expression and protein production of the NF-kappaB-dependent cytokines TNF-alpha and IL-1beta and the chemokine CCL21 in the skin. The decreases in these cytokines resulted in reduced migration of allergen-presenting dendritic cells from the skin into skin-draining lymph nodes and markedly decreased activation of effector CD8+ T cells for the CHS response to allergen challenge (inhibitory concentration 50% or IC50 was 55 mg/kg). These findings reveal a previously unrecognized mechanism of QC-mediated inhibition of inflammation.     

Epidermal NLRP10 contributes to contact hypersensitivity responses in mice

The nucleotide binding and oligomerization domain‐like receptor (NLR) protein NLRP10 is highly expressed in the epidermis and contributes to cell‐autonomous responses against invasive bacteria. To investigate the role of NLRP10 in inflammatory responses of the skin we analyzed the effect of full‐body and keratinocyte‐specific depletion of NLRP10 in croton oil‐induced irritant contact dermatitis (ICD) and 1‐fluoro‐2,4‐dinitrobenzene (DNFB)‐induced contact hypersensitivity (CHS) in mice. Nlrp10^?/? mice were phenotypically normal and skin repair after wounding was not affected by lack of NLRP10. Similarly, we did not detect a contribution of NLRP10 to the ICD response induced by croton oil. In contrast, Nlrp10^?/? mice showed significantly reduced inflammation in the DNFB‐induced CHS response as compared to control animals. Microscopic analysis revealed significantly reduced numbers of CD4⁺ and CD8⁺ T cells in the infiltrates of animals lacking NLRP10 expression after CHS challenge. Epidermis‐specific deletion of Nlrp10 by keratin‐14 promotor driven Cre‐recombinase was sufficient to account for this phenotype, although lymphocyte recruitment seemed to be unaltered in animals lacking NLRP10 expression in keratinocytes. Taken together, we provide evidence that NLRP10 contributes to T‐cell‐mediated inflammatory responses in the skin and highlight a physiological role of NLRP10 in epidermal keratinocytes.     

Langerhans' cells produce type IV collagenase (MMP-9) following epicutaneous stimulation with haptens.

For initiation of the contact hypersensitivity response, epidermal Langerhans' cells (LC) migrate from the epidermis to draining nodes via afferent lymphatics by passing through the basement membrane. In this study, we examined production of matrix metalloproteinases (MMPs) in LC-enriched epidermal cells to clarify the type of enzymes involved in LC transmigration through the basement membrane. Using gelatine enzymography and immunoblotting analysis, 95,000 MW type IV collagenase (MMP-9) was found to be produced by LC-enriched epidermal cells. Analysis of the kinetics of MMP-9 expression showed that its production was induced within 6 hr after application of 2,4,6-trinitrochlorobenzene (TNCB), substantially increased between 12 hr and 24 hr, and then decreased to the normal level by 7 to 10 days. Other haptens, such as 2,4-dinitrochlorobenzene and 2,4-dinitrofluorobenzene, also induced MMP-9 expression. Fluoroescence-activated cell sorter analysis revealed that LC were one of the major cell types to express MMP-9 in response to TNCB. In addition, highly enriched LC from sensitized skin were shown to express strong gelatinolytic activity. These results indicate that LC by themselves, as well as other epidermal cells, are capable of producing MMP-9, and suggest that MMP-9 may contribute to proteolysis associated with transmigration of LC in the induction phase of contact dermatitis.     

The role of interleukin-16 in murine contact hypersensitivity

Contact hypersensitivity (CHS) is a T-cell-mediated skin inflammatory response. It is controversial whether CD4(+) T cells play an enhancing or regulatory role in the pathogenesis of CHS. Because interleukin (IL)-16 is a chemoattractant cytokine for CD4-expressing cells, we investigated the involvement of IL-16 in the CHS reaction. IL-16 production was induced in the epidermis and dermis during the elicitation phase of the CHS response with trinitrochlorobenzene. In the sensitization phase, the single application of haptens such as trinitrochlorobenzene and oxazolone also induced IL-16, whereas primary irritants or vehicle control did not. IL-16 was produced mainly by CD11c-negative cells in the epidermis during the elicitation phase. Furthermore, treatment of sensitized mice with anti-IL-16 neutralizing MoAb enhanced the ear swelling and reduced the number of infiltrating CD4(+) T cells. These data indicate that IL-16 plays a role in CHS, whereby IL-16 induces CD4(+) T cells and these CD4(+) T cells subsequently exhibit down-regulating properties.     

Reduced 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity response in IL-15 receptor alpha-deficient mice correlates with diminished CCL5/RANTES and CXCL10/IP-10 expression

Using a model of 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity (CHS) we found that, as compared with wild-type mice, IL-15 receptor alpha chain (IL-15Ralpha)-deficient mice showed significantly less ear swelling. This decreased response was associated with diminished expression of CCL5/RANTES and CXCL10/IP-10, chemokines critical for effector cell recruitment, in the inflamed tissue. We determined that both the number of CD8(+) T cells infiltrating the affected skin and the production of CCL5/RANTES by antigen-stimulated CD8(+) T cells were decreased in IL-15Ralpha(-/-) mice. The lower levels of CXCL10/IP-10 suggested that the IL-15Ralpha(-/-) mice had reduced production of IFN-gamma, the primary inducer of CXCL10/IP-10, which was in fact the case. However, by contrast with CCL5/RANTES, the diminished levels of IFN-gamma were likely due to the decreased number of skin-infiltrating CD8(+) T cells, since IFN-gamma production by antigen-stimulated CD8(+) T cells was comparable between wild-type and IL-15Ralpha(-/-) mice. Our data suggest a positive, pro-inflammatory feedback loop involving CCL5/RANTES, IFN-gamma and CXCL10/IP-10 that underlies the CHS reaction and that is disrupted, likely primarily by a defect in CCL5/RANTES production, in mice lacking IL-15Ralpha, resulting in impaired leukocyte recruitment and inflammation. Moreover, it is particularly noteworthy that the defect in CCL5/RANTES expression in CD8(+) T cells is intrinsic to the absence of IL-15Ralpha, indicating that IL-15Ralpha is critical for CCL5/RANTES expression in CD8(+) T cells.