Cytokine gene expression during the elicitation phase of contact sensitivity: regulation by endogenous IL-4

Lithraea caustic (Litre) Extract Promotes an Antitumor Response Against B16 Melanoma

Melanoma immunotherapy, specifically the autotransplant of dendritic cells charged with tumors antigens, has shown promising results in clinical trials. The positive clinical effects of this therapy have been associated to increased Th17 response and delayed-type hypersensitivity (DTH) against to tumor antigens. Some synthetic compounds, such as diphenylcyclopropenone (DPCP), are capable of triggering a DTH response in cutaneous malignancies and also to induce clinically relevant effects against melanoma. In this work, we evaluated Litre extract (LExT), a standardized extract of a Chilean stinging plant, Lithraea caustic (Litre). As Litre plant is known to induce DTH, we used a murine B16 melanoma model to compare the topical and intratumor efficacy of LExT with synthetic DTH inducers (DPCP and 2,4-dinitrochlorobenzene [DNCB]). LExt contained mainly long chain catechols and sesquiterpenes. The intratumor injection of LExT induced a significant delay in tumor growth, similarly topical treatment of an established tumor with 0.1% LExT ointment induced a growth delay and even tumor regression in 15% of treated animals. No significant changes were observed on the T-cell populations associated to LExT treatment, and neither DNCB nor DPCP were capable to induce none of the LExT-induced antitumoral effects. Interestingly, our results indicate that LExT induces an antitumor response against melanoma in a mouse model and could bring a new –and affordable- treatment for melanoma in humans.

Endogenous N-acyl taurines regulate skin wound healing

The intracellular serine amidase, fatty acid amide hydrolase (FAAH), degrades a heterogeneous family of lipid-derived bioactive molecules that include amides of long-chain fatty acids with taurine [N-acyl-taurines (NATs)]. The physiological functions of the NATs are unknown. Here we show that genetic or pharmacological disruption of FAAH activity accelerates skin wound healing in mice and stimulates motogenesis of human keratinocytes and differentiation of human fibroblasts in primary cultures. Using untargeted and targeted lipidomics strategies, we identify two long-chain saturated NATs-N-tetracosanoyl-taurine [NAT(24:0)] and N-eicosanoyl-taurine [NAT(20:0)]-as primary substrates for FAAH in mouse skin, and show that the levels of these substances sharply decrease at the margins of a freshly inflicted wound to increase again as healing begins. Additionally, we demonstrate that local administration of synthetic NATs accelerates wound closure in mice and stimulates repair-associated responses in primary cultures of human keratinocytes and fibroblasts, through a mechanism that involves tyrosine phosphorylation of the epidermal growth factor receptor and an increase in intracellular calcium levels, under the permissive control of transient receptor potential vanilloid-1 receptors. The results point to FAAH-regulated NAT signaling as an unprecedented lipid-based mechanism of wound-healing control in mammalian skin, which might be targeted for chronic wound therapy.

Histone deacetylase 6 inhibition impairs effector CD8 T-cell functions during skin inflammation

BACKGROUND

Broad-spectrum histone deacetylase (HDAC) inhibitors are useful in the treatment of allergic and autoimmune diseases and malignancy. However, use of more specific HDAC inhibitors might limit the toxicities caused by HDAC inhibition. HDAC6, a member of the HDAC family, is highly expressed on CD8 T cells and has been shown to regulate immune responses through interactions between T cells and antigen-presenting cells. However, the mechanism by which HDAC6 inhibition affects the activation and functions of CD8 T cells is unclear.

OBJECTIVES

We investigated the role or roles of HDAC6 in CD8 T-cell activation and functions during skin inflammation in vitro and in vivo and examined the mechanism by which HDAC6 inhibition modifies T-cell receptor signaling in vitro.

METHODS

We assessed the clinical and biological effects of ACY-1215, an HDAC6-specific inhibitor, by using murine CD8 T cell-related skin disease models, including contact hypersensitivity (CHS) and experimental graft-versus-host disease (GVHD)-like disease.

RESULTS

ACY-1215, an HDAC6 inhibitor, prevented the development of CHS and GVHD-like disease in vivo by modulating CD8 T-cell activation and functions; abrogated the induction of effector T cells from naive CD8 T cells by means of anti-CD3/CD28 antibody- or antigen-specific stimulation in vitro; and enhanced the binding of acetylated heat shock protein 90 to lymphocyte-specific protein tyrosine kinase in vitro, disrupting lymphocyte-specific protein tyrosine kinase phosphorylation and leading to impairment of the mitogen-activated protein kinase pathway.

CONCLUSION

HDAC6, a key modifier of T-cell receptor signaling, might represent a novel target for the treatment of CD8 T cell-related skin diseases, including CHS and GVHD.

Update of immune events in the murine contact hypersensitivity model: toward the understanding of allergic contact dermatitis

Allergic contact dermatitis (ACD) is one of the most common skin diseases, consisting of sensitization and elicitation phases. With the advancement of technology and the discovery of new types of immune cells, our knowledge of the immunological mechanisms of contact hypersensitivity (CHS) as a murine model of ACD has expanded significantly in the past decade. For example, by introducing regulatory T cells, CD4(+) T-helper 17 cells, and Langerin-positive dermal dendritic cells, the initiation and termination mechanism of CHS has been revealed. In addition, the role of mast cells in CHS, long a matter of debate, has become apparent by developing conditional mast cell-deficient mice. Moreover, the role of the innate immunity system, such as that of Toll-like receptor signaling, has made a breakthrough in this field. In this review, we will integrate the recent advancement of immunological mechanisms of both the sensitization and elicitation phases of CHS into the classic view, and we will discuss updated mechanisms on its development and future directions.

Gene silencing of STAT6 with siRNA ameliorates contact hypersensitivity and allergic rhinitis

BACKGROUND

Silencing of genes using small interfering RNA (siRNA) is a recently developed strategy to regulate the synthesis of target molecules. Signal transducer and activator of transcription 6 (STAT6) is a nuclear transcription factor that mediates Th2-type immunity.

METHODS

To elucidate the therapeutic potential of using siRNA to inhibit STAT6 in allergic reactions, we determined the nucleotide sequences of siRNA specific for STAT6.

RESULTS

The selected sequences of STAT6 siRNA specifically inhibited the generation of STAT6 synthesis in dermal fibroblasts and eotaxin (CCL11) production in response to IL-4/TNF-α in vitro. Local administration of STAT6 siRNA in vivo alleviated contact hypersensitivity responses to chemical haptens. This was accompanied by reduced local production of IL-4, IL-13, eotaxin (CCL11), TARC (CCL17) and MDC (CCL22). Similarly, consecutive intranasal instillation of STAT6 siRNA markedly inhibited inflammatory cellular infiltration of mucosal tissues in allergic rhinitis responses in association with reduced IL-4 and IL-5 production from regional lymph node cells. Immediate responses, such as sneezing and nasal rubbing behaviors, were also improved by STAT6 siRNA.

CONCLUSIONS

Local administration of STAT6 siRNA is thus a promising therapeutic strategy for both Th2-mediated cutaneous diseases and allergic rhinitis.

Effect of Formaldehyde Gas Exposure in a Murine Allergic Contact Hypersensitivity Model

To clarify the effect of formaldehyde (FA) gas exposure on contact hypersensitivity (CHS), CHS reactions against 2,4,6-trinitrochlorobenzene (TNCB) was studied in BALB/c mice with a low dose of FA gas exposure. The TNCB-induced CHS reactions were slightly suppressed by the FA gas exposure immediately after sensitization, whereas they were significantly enhanced and prolonged in mice continuously exposed to FA gas before and after sensitization. We showed that exposure to FA gas enhanced the Th2 dominant responses in draining lymph node (LN) in early stage of CHS. In contrast, T cell subsets and their intracellular cytokine production in the draining LN were similar during the early stage of CHS by FA gas exposure during the sensitization phase. The percentage of CD8+ T cells was increased, and the percentage of CD4+CD25+ T cells was decreased in the FA gas-exposed group at 72 hr after elicitation. These results indicate that FA gas-exposed might influence regulatory T cells. Furthermore, in the chronic CHS model that was repetitively elicited with TNCB, more intensive and prolonged CHS reactions, and increased numbers of mast cells were found in the FA gas-exposed group at 4 hr after elicitation than in the control group, FA gas exposure may alter the intensity of allergic CHS.

Staphylococcal enterotoxin B enhances a flare-up reaction of murine contact hypersensitivity through up-regulation of interferon-gamma

BACKGROUND

We often see aggravation of eczematous skin lesions associated with bacterial infection, but the mechanism of this phenomenon is unclear. Staphylococcus aureus is known to colonize on the eczematous lesion and produce some exotoxins, which act as bacterial superantigens.

OBJECTIVES

To investigate the potential role of superantigens in chronic dermatitis, we investigated the effect of staphylococcal enterotoxin B (SEB) on the skin reaction, the proliferative response and the cytokine production of local lymph node cells in the mouse model of contact hypersensitivity reaction.

METHODS

Sensitized BALB/c mice were repeatedly challenged with dinitrofluorobenzene (DNFB), and intravenously injected with SEB and dinitrobenzne sulfonic acid sodium salt (DNBS). The ear swelling response was measured after DNBS injection. Cervical lymph node cells of those mice were cultured with DNBS in vitro. Their proliferative responses and the production of cytokines were assessed.

RESULTS

SEB markedly enhanced the flare-up reaction of ear swelling induced by DNBS, the proliferative response of lymph node cells and the production of IFN-gamma. In contrast, the production of IL-5 was decreased.

CONCLUSIONS

The present study may provide some clues for elucidating the mechanism involved in the exacerbation of dermatitis associated with staphylococcal infection.

Th1 and type 1 cytotoxic T cells dominate responses in T-bet overexpression transgenic mice that develop contact dermatitis

Contact dermatitis in humans and contact hypersensitivity (CHS) in animal models are delayed-type hypersensitivity reactions mediated by hapten-specific T cells. Recently, it has become clear that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T (Tc1) cells can act as effectors in CHS reactions. T-bet has been demonstrated to play an important role in Th1 and Tc1 cell differentiation, but little is known about its contribution to CHS. In the present study, we used C57BL/6 mice transgenic (Tg) for T-bet to address this issue. These Tg mice, which overexpressed T-bet in their T lymphocytes, developed dermatitis characterized by swollen, flaky, and scaly skin in regions without body hair. Skin histology showed epidermal hyperkeratosis, neutrophil, and lymphocyte infiltration similar to that seen in contact dermatitis. T-bet overexpression in Tg mice led to elevated Th1 Ig (IgG2a) and decreased Th2 Ig (IgG1) production. Intracellular cytokine analyses demonstrated that IFN-gamma was increased in both Th1 and Tc1 cells. Furthermore, Tg mice had hypersensitive responses to 2,4-dinitrofluorobenzene, which is used for CHS induction. These results suggest that the level of expression of T-bet might play an important role in the development of contact dermatitis and that these Tg mice should be a useful model for contact dermatitis.

Itraconazole suppresses an elicitation phase of a contact hypersensitivity reaction

Contact dermatitis is caused by epicutaneous exposure to environmentally and/or industrially derived allergens. As the exposure is unavoidable in many instances, therapeutic suppression of allergic inflammation appears to be of clinical relevance. It was recently reported that itraconazole (ITZ), an anti-fungal agent, may be of therapeutic importance in allergic skin diseases. Therefore, we were interested in the effect of ITZ on contact hypersensitivity (CHS). Mice (C3H/HeN or Balb/c) were administered with ITZ orally before sensitization or challenged with haptens (dinitrofluorobenzene or oxazolone). Consequently, the administration of ITZ before challenge, but not before sensitization, significantly suppressed the reaction. Intriguingly, ITZ failed to suppress the irritant dermatitis induced by croton oil or benzalkonium chloride, suggesting that it may affect molecule(s) rather selectively involved in the elicitation of CHS. To further analyze mechanisms involved, splenic T cells obtained from sensitized or naive mice were stimulated with plate-bound anti-CD3 in the presence or absence of ITZ and release of cytokines was tested by ELISA. T cells from hapten-immunized mice produced a significant amount of IFN-gamma, which was markedly suppressed by ITZ. Our study demonstrates that ITZ selectively suppresses the elicitation phase of CHS possibly via downmodulation of IFN-gamma.

Evidence for a novel protective role of the vanilloid TRPV1 receptor in a cutaneous contact allergic dermatitis model

The purpose of this study was to examine the involvement of the transient receptor potential vanilloid receptor 1 (TRPV1) in inflammatory processes observed in murine allergic contact dermatitis (ACD). Oxazolone-induced ACD evoked a significant ear swelling after 24-72 h. It was augmented in TRPV1 knockout mice at all time points and supported by histological analysis and measure of TNF-alpha. However, tissue swelling and cytokine generation was significantly reduced in both neurokinin 1 receptor and calcitonin gene-related peptide (CGRP) knockout mice. A protective involvement of the TRPV1 receptor was identified of contact dermatitis distinct from mechanisms involving the major pro-inflammatory neuropeptides.

Molecular biology of the 3beta-hydroxysteroid dehydrogenase/delta5-delta4 isomerase gene family

The 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4) isomerase (3beta-HSD) isoenzymes are responsible for the oxidation and isomerization of Delta(5)-3beta-hydroxysteroid precursors into Delta(4)-ketosteroids, thus catalyzing an essential step in the formation of all classes of active steroid hormones. In humans, expression of the type I isoenzyme accounts for the 3beta-HSD activity found in placenta and peripheral tissues, whereas the type II 3beta-HSD isoenzyme is predominantly expressed in the adrenal gland, ovary, and testis, and its deficiency is responsible for a rare form of congenital adrenal hyperplasia. Phylogeny analyses of the 3beta-HSD gene family strongly suggest that the need for different 3beta-HSD genes occurred very late in mammals, with subsequent evolution in a similar manner in other lineages. Therefore, to a large extent, the 3beta-HSD gene family should have evolved to facilitate differential patterns of tissue- and cell-specific expression and regulation involving multiple signal transduction pathways, which are activated by several growth factors, steroids, and cytokines. Recent studies indicate that HSD3B2 gene regulation involves the orphan nuclear receptors steroidogenic factor-1 and dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome gene 1 (DAX-1). Other findings suggest a potential regulatory role for STAT5 and STAT6 in transcriptional activation of HSD3B2 promoter. It was shown that epidermal growth factor (EGF) requires intact STAT5; on the other hand IL-4 induces HSD3B1 gene expression, along with IL-13, through STAT 6 activation. However, evidence suggests that multiple signal transduction pathways are involved in IL-4 mediated HSD3B1 gene expression. Indeed, a better understanding of the transcriptional factors responsible for the fine control of 3beta-HSD gene expression may provide insight into mechanisms involved in the functional cooperation between STATs and nuclear receptors as well as their potential interaction with other signaling transduction pathways such as GATA proteins. Finally, the elucidation of the molecular basis of 3beta-HSD deficiency has highlighted the fact that mutations in the HSD3B2 gene can result in a wide spectrum of molecular repercussions, which are associated with the different phenotypic manifestations of classical 3beta-HSD deficiency and also provide valuable information concerning the structure-function relationships of the 3beta-HSD superfamily. Furthermore, several recent studies using type I and type II purified enzymes have elegantly further characterized structure-function relationships responsible for kinetic differences and coenzyme specificity.

In vivo transfection of a cis element 'decoy' against signal transducers and activators of the transcription 6 (STAT6) binding site ameliorates the response of contact hypersensitivity

We herein demonstrate that STAT6 plays an important role in the induction of not only acute contact hypersensitivity (CHS), but also chronic CHS in a mouse model using STAT6-deficient (STAT6(-/-)) mice. We, therefore, determine whether synthetic double-stranded DNA with a high affinity for STAT6 can be introduced in vivo as a decoy cis element to bind the transcriptional factor and block the induction of not only acute CHS but also chronic CHS. Treatment by the transfection of STAT6 decoy oligodeoxynucleotides (ODN), after the induction of 2,4,6-trinitrochlorobenzene or other haptens had a significant inhibitory effect on the induction of both acute CHS and chronic CHS. We thus examined the mechanism of the in vivo effect of the transfection of STAT6 decoy ODN in both acute and chronic CHS. In the histological analysis, the infiltration of eosinophils and degranulated mast cells, and the production of IL-4, IL-6 and eotaxin, but not IFN-gamma in the extracts from challenged skin significantly decreased by the transfection of STAT6 decoy ODN. We herein report the first successful in vivo transfer of STAT6 decoy ODN to inhibit acute and chronic CHS, thus providing a new therapeutic strategy not only for the treatment of CHS but also for atopic dermatitis.

Fas-Mediated Inhibition of CD4+ T Cell Priming Results in Dominance of Type 1 CD8+ T Cells in the Immune Response to the Contact Sensitizer Trinitrophenyl

One of the unusual properties of chemically reactive haptens is their capacity to simultaneously generate immunogenic determinants for hapten-specific CD8(+) and CD4(+) T cells. Surprisingly, however, a clear dominance of CD8(+) effector T cells is observed in murine contact hypersensitivity to various haptens and upon T cell priming with hapten-modified APCs in vitro. In this study we show that trinitrophenyl-specific CD8(+) T cells actively prevent CD4(+) T cell priming in vitro. This process requires cell-cell contact and is dependent on the expression of Fas on the CD4(+) T cells. Our results reveal an important Fas-dependent mechanism for the regulation of hapten-specific CD4(+) T cell responses by CD8(+) T cells, which causes the dominance of CD8(+) effector T cells and the active suppression of a CD4(+) T cell response. Moreover, our demonstration of reduced contact hypersensitivity to trinitrophenyl in the absence of Fas, but not of perforin and/or granzymes A and B, underlines the important role of Fas as a pathogenetic factor for contact hypersensitivity.

T Lymphocyte-Mediated Immune Responses to Chemical Haptens and Metal Ions: Implications for Allergic and Autoimmune Disease

Chemical haptens and metal ions interact with proteins and thereby become recognizable by T and B lymphocytes. They induce the production of proinflammatory cytokines and chemokines by various cell types due to triggering of innate immune responses. This is an important prerequisite for the activation of the adaptive immune system and the development of diseases like allergic contact dermatitis and adverse drug and autoimmune reactions. Our increasing knowledge about the molecular basis of hapten and metal ion recognition by T cells and about the pathomechanisms of contact hypersensitivity and chemical-induced autoimmune reactions allows concomitant progress in the development of modern strategies for immunotherapy and will hopefully enable more specific intervention in hapten- and metal ion-induced human diseases in the future.

Impaired responses of peripheral blood mononuclear cells to nickel in patients with nickel-allergic contact dermatitis and concomitant atopic dermatitis

BACKGROUND

Allergic contact dermatitis (ACD) is pathogenetically dependent on cell-mediated immune responses mediated by type 1 T lymphocytes. Atopic dermatitis (AD), in contrast, occurs as a result of sustained activation of type 2 subsets of T cells. Although atopic patients may become sensitized to various contact allergens, little is known about the influence of atopy on delayed-type hypersensitivity.

OBJECTIVES

To investigate the in vitro responses of peripheral blood mononuclear cells (PBMC) to nickel stimulation in groups of atopic and nonatopic patients with patch test-verified nickel ACD.

METHODS

Ten nonatopic patients with nickel ACD, 10 patients with nickel ACD and concomitant AD, 10 patients with AD but with no contact allergy, and 10 healthy persons participated in the study. PBMC were cultured in the presence or absence of nickel sulphate, phytohaemagglutinin (PHA) or tetanus toxoid (TT). [(3)H]thymidine incorporation was used to measure the rate of antigen-induced DNA synthesis and enzyme-linked immunosorbent assay was used to measure the production of interleukin (IL)-2 (type 1 cytokine) and IL-5 (type 2 cytokine).

RESULTS

Nickel-stimulated PBMC of nickel-allergic patients with AD proliferated significantly less and secreted significantly lower amounts of IL-2 than cells of nonatopic nickel-allergic patients. IL-5 production was also lower in the former group, although the difference was nonsignificant. Moreover, neither the nickel-specific DNA synthesis nor the cytokine production by PBMC of atopic nickel-allergic patients differed significantly from those of healthy control persons and AD patients without contact allergy. Proliferative and secretory responses of PBMC to PHA or TT stimulation differed nonsignificantly between the groups. Nickel-induced IL-2 production correlated well with IL-5 production in nickel-allergic patients regardless of their atopic status.

CONCLUSIONS

Our results indicate that PBMC of nickel-allergic patients with concomitant AD are characterized by impaired in vitro proliferative and secretory responses to the contact allergen nickel but not to the mitogen PHA or the recall antigen TT. The type 2 cytokine IL-5 may play a role in the development of ACD.

CD4+ T Cells Regulate CD8+ T Cell-Mediated Cutaneous Immune Responses by Restricting Effector T Cell Development through a Fas Ligand-Dependent Mechanism

The magnitude and duration of CD8(+) T cell-mediated responses in the skin to hapten sensitization and challenge, contact hypersensitivity (CHS), is negatively regulated by CD4(+) T cells through an unknown mechanism. In this study we show that CD4(+) T cells restrict the development and expansion of hapten-specific CD8(+) T cells mediating CHS responses to 2,4-dinitrofluorobenzene. In the absence of CD4(+) T cells, high numbers of hapten-specific CD8(+) T cells producing IFN-gamma were detected in the skin-draining lymph nodes on day 5 postsensitization, and these numbers decreased slightly, but were maintained through day 9, correlating with the increased magnitude and duration of CHS responses observed in these mice. In the presence of CD4(+) T cells, the number of hapten-specific CD8(+) T cells producing IFN-gamma detected on day 5 postsensitization was lower and quickly fell to background levels by day 7. The limited development of effector CD8(+) T cells was associated with decreased numbers of hapten-presenting dendritic cells in the lymphoid priming site. This form of immunoregulation was absent after sensitization of Fas ligand-defective gld mice. Transfer of wild-type CD4(+) T cells to gld mice restored the negative regulation of CD8(+) T cell priming and the immune response to hapten challenge in gld-recipient mice. These results indicate that CD4(+) T cells restrict hapten-specific CD8(+) T cell priming for CHS responses through a Fas ligand-dependent mechanism.

Cytokine knockouts in contact hypersensitivity research

Contact hypersensitivity (CHS) is a Langerhans cell (LC)-dependent, T cell-mediated cutaneous immune response. CHS reflects a culmination of LC activities in vivo: uptake of epicutaneous antigens, migration into lymph nodes, and presentation of antigens to naïve T cells. Although studies have suggested involvement of the cytokine network in LC migration and CHS initiation, the in vivo function of individual cytokines remains largely unknown. Gene targeting technology has made it possible to study in vivo functions of cytokines through gene-targeted knockout (KO) mice deficient in a given cytokine or its receptor. A variety of cytokine knockouts have been used to assign biological functions to specific cytokines in CHS. These studies have contributed significantly to our understanding of molecular mechanisms underlying CHS.

Suplatast tosilate inhibits eosinophil production and recruitment into the skin in murine contact sensitivity

Antiallergic drugs and antihistamines have been widely used for controlling mucosal allergic diseases in which eosinophilia is prominent. Although H1-receptor antagonists are effective for treating histamine-induced wheal and itch in urticaria, the effects of antihistamines and antiallergic agents on other eosinophilic skin diseases remain to be determined. We investigated the effects of oral administration of antiallergic drugs and antihistamines, such as suplatast tosilate, emedastine difumarate, and azelastine hydrochloride, on a novel murine model of eosinophilia in contact sensitivity to picryl chloride. Among the drugs tested, only suplatast tosilate remarkably inhibited blood and tissue eosinophilia and the ear swelling responses. The inhibitory effects on eosinophilia seemed to be mediated by the suppression of IL-5 production in spleen cells during eosinophil development, while the effects on the ear swelling response seemed to be mediated by suppression of IL-4 production in immune lymph node cells in the efferent phase. Suplatast tosilate may effectively treat eosinophilic skin diseases in which Th2-cell-derived cytokines are predominant.

Expression of cytokine mRNAs in mice cutaneously exposed to formaldehyde

In this study, we have investigated the expression of cytokine mRNAs in mice cutaneously exposed to formaldehyde using semiquantitative RT-PCR. We show that formaldehyde induced the long-lasting expression of IL-4 and IFN-gamma mRNAs and the transient expression of IL-13 mRNA in mouse spleen and draining lymph nodes. The transient increases in IL-2, IL-15, IL-12p40, IL-15 and IL-18 mRNAs, but long-lasting IL-15 mRNA were only seen in the formaldehyde-exposed mouse spleen. Moreover, a weak contact hypersensitivity (CH) and the significant increases in IL-4 and IFN-gamma mRNAs were detected in the ear skin of formaldehyde-cutaneously exposed mice when rechallenged mouse ears. Furthermore, CH as measured by mouse ear swelling response was positively correlated with IL-4 and IFN-gamma mRNA levels in the challenged ears. This study thus suggests that the induction of Th1 and Th2 cytokine mRNAs, particularly IL-4 and IFN-gamma, are a common immunological feature caused by contact allergens irrespective of strong or weak contact allergens. The analysis of IL-4 and IFN-gamma mRNAs may be useful markers in establishing the novel test for predicting chemical sensitizing potentials.

Crucial role of cytokines in sex steroid formation in normal and tumoral tissues

There is evidence suggesting that local intracrine formation of sex steroids from inactive precursors, dehydroepiandrosterone (DHEA), its sulfate (DHEA-S) and 4-androstenedione (4-DIONE) plays an important role in the regulation of growth and function of peripheral target tissues. Moreover, human solid tumors are often infiltrated by stromal/immune cells secreting a wide spectra of cytokines. These cytokines might in turn regulate the activity of both immune and neoplastic cells. Our data demonstrate that the potent regulatory effects of interleukin-4 (IL-4) and IL-6 on both estrogenic and androgenic 17beta-HSD/KSR activities in breast cancer cells depend on the cell-specific gene expression of various types of 17beta-HSD/KSR enzymes. However, in both estrogen-receptor (ER)-positive (ZR-75-1, T-47D) and ER-negative (MDA-MB-231, BT-20) human breast cancer cells, exposure to IL-4 and IL-13 caused a rapid and potent induction of 3beta-HSD type 1 gene expression. Such an induction was also observed in normal human mammary and prostate epithelial cells in primary culture as well as in human HaCaT immortalized keratinocytes, ME-180 cervix cancer cells, and HT-29 colon cancer cells. The DNA-binding activity of Stat6, a member of the Signal Transducers and Activators of Transcription gene family, was activated after a 30 min exposure to IL-4 in all the cell types where IL-4 induced 3beta-HSD expression, but not in those that failed to respond to IL-4. Our data therefore suggest that IL-4 and IL-13 may play a role in the biosynthesis of active sex steroids from the inactive adrenal steroid DHEA, not only in breast cells but also in various cell types derived from peripheral target tissues.

CD4+ Th1 and CD8+ type 1 cytotoxic T cells both play a crucial role in the full development of contact hypersensitivity

The role of CD4(+) vs CD8(+) T cells in contact hypersensitivity (CHS) remains controversial. In this study, we used gene knockout (KO) mice deficient in CD4(+) or CD8(+) T cells to directly address this issue. Mice lacking either CD4(+) or CD8(+) T cells demonstrated depressed CHS responses to dinitrofluorobenzene and oxazolone compared with wild-type C57BL/6 mice. The depression of CHS was more significant in CD8 KO mice than in CD4 KO mice. Furthermore, in vivo depletion of either CD8(+) T cells from CD4 KO mice or CD4(+) T cells from CD8 KO mice virtually abolished CHS responses. Lymph node cells (LNCs) from hapten-sensitized CD4 and CD8 KO mice showed a decreased capacity for transferring CHS. In vitro depletion of either CD4(+) T cells from CD8 KO LNCs or CD8(+) T cells from CD4 KO LNCs resulted in a complete loss of CHS transfer. LNCs from CD4 and CD8 KO mice produced significant amounts of IFN-gamma, indicating that both CD4(+) and CD8(+) T cells are able to secrete IFN-gamma. LNCs from CD8, but not CD4, KO mice were able to produce IL-4 and IL-10, suggesting that IL-4 and IL-10 are mainly derived from CD4(+) T cells. Intracellular cytokine staining of LNCs confirmed that IFN-gamma-positive cells consisted of CD4(+) (Th1) and CD8(+) (type 1 cytotoxic T) T cells, whereas IL-10-positive cells were exclusively CD4(+) (Th2) T cells. Collectively, these results suggest that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T cells are crucial effector cells in CHS responses to dinitrofluorobenzene and oxazolone in C57BL/6 mice.

Role of CD4(+) T helper 2-type cells in cutaneous inflammatory responses induced by fluorescein isothiocyanate

Owing to its skin-sensitizing and fluorochromatic properties, fluorescein isothiocyanate (FITC) is employed frequently as an experimental hapten in mechanistic studies of contact allergy, particularly in the context of the role of migration and activation of Langerhans' cells. In this study we demonstrated that topical exposure of mice to FITC results in the selective development of activated lymph node cells (LNC) expressing a preferential type 2 cytokine-secretion profile, with high levels of interleukin (IL)-4 and IL-10, but low levels of interferon-gamma (IFN-gamma). Negative selection (complement depletion) identified CD4(+) T helper (Th)2-type cells as the primary source in activated LNC of the type 2 cytokines IL-4 and IL-10, whereas the low levels of IFN-gamma produced were derived exclusively from CD8(+) T cytotoxic (Tc) 1-type cells. A biphasic pattern of cutaneous inflammatory reactions was elicited by exposure to FITC, the early phase of which could be transferred passively with serum (presumably immunoglobulin E [IgE] antibody), whereas adoptive transfer experiments demonstrated that Th2-type CD4(+) cells were responsible for the delayed-type component of the dermal hypersensitivity reaction. In contrast with contact allergic reactions induced by other sensitizing haptens, which are considered to be largely Th1/Tc1-mediated immune processes regulated by Th2-type cells, these results suggest therefore that the skin lesions provoked in mice by FITC are primarily a result of the activation of Th2-type cells.

Restraint-induced modulation of allergic and irritant contact dermatitis in male and female B6.129 mice

Recent studies in rats have indicated that acute restraint enhances cutaneous hypersensitivity. We hypothesized that acute restraint would also modulate the development of allergic and irritant dermatitis in mice and that these restraint-induced changes would be reflected in the cutaneous cytokine profile and be gender-specific. For these studies, male and female B6.129 mice were sensitized and challenged with the contact sensitizer dinitrofluorobenzene or challenged with the irritant croton oil. Two-hour restraint was applied prior to chemical challenge. Restraint combined with chemical increased ear swelling in both genders in ACD, a change that was blocked by administration of RU-486 prior to restraint. Neither restraint nor RU-486 administration modulated development of ICD; however, IL-1beta was decreased by restraint in females only. TNF-alpha and IFN-gamma production were modified in ACD; TNF-alpha in both genders and IFN-gamma in female mice only. Our data demonstrate that acute restraint increases serum corticosterone in B6.129 male and female mice to comparable levels. Restraint modulated the murine ear swelling in ACD, but not ICD, in both genders, and the change in the ear swelling response and cytokine production were, at least in part, corticosterone-dependent.

Mast cells control neutrophil recruitment during T cell-mediated delayed-type hypersensitivity reactions through tumor necrosis factor and macrophage inflammatory protein 2

Polymorphonuclear leukocytes (PMNs) characterize the pathology of T cell-mediated autoimmune diseases and delayed-type hypersensitivity reactions (DTHRs) in the skin, joints, and gut, but are absent in T cell-mediated autoimmune diseases of the brain or pancreas. All of these reactions are mediated by interferon gamma-producing type 1 T cells and produce a similar pattern of cytokines. Thus, the cells and mediators responsible for the PMN recruitment into skin, joints, or gut during DTHRs remain unknown. Analyzing hapten-induced DTHRs of the skin, we found that mast cells determine the T cell-dependent PMN recruitment through two mediators, tumor necrosis factor (TNF) and the CXC chemokine macrophage inflammatory protein 2 (MIP-2), the functional analogue of human interleukin 8. Extractable MIP-2 protein was abundant during DTHRs in and around mast cells of wild-type (WT) mice but absent in mast cell-deficient WBB6F(1)-Kit(W)/Kit(W-)(v) (Kit(W)/Kit(W)(-v)) mice. T cell-dependent PMN recruitment was reduced >60% by anti-MIP-2 antibodies and >80% in mast cell-deficient Kit(W)/Kit(W)(-v) mice. Mast cells from WT mice efficiently restored DTHRs and MIP-2-dependent PMN recruitment in Kit(W)/Kit(W)-(v) mice, whereas mast cells from TNF(-/)- mice did not. Thus, mast cell-derived TNF and MIP-2 ultimately determine the pattern of infiltrating cells during T cell-mediated DTHRs.

New insights into the pathomechanisms of contact dermatitis by the use of transgenic mouse models

Allergic contact dermatitis (ACD) is one of the most common skin diseases with a great socioeconomic impact. Although extensively studied, its pathophysiology and the interaction of different cells and factors which lead to sensitization and elicitation reaction are still not completely understood. The advent of transgenic mouse technology has considerably changed the study of ACD. This technology has been used extensively to investigate biomedically important issues in such diverse areas as mammalian development, neurophysiology and immunology. This new approach has already led to fascinating results which are confirmatory but also contradictory to previous thinking on the role of certain cytokines, adhesion and cell surface molecules in the complex pathophysiologic process of ACD. This review will describe how recent experiments employing mice carrying cytokine and accessory molecule transgenes change our current understanding of contact dermatitis which may lead to improved therapeutic strategies.

Disparate cytotoxic activity of nickel-specific CD8+ and CD4+ T cell subsets against keratinocytes

Allergic contact dermatitis (ACD) is the result of an exaggerated immune reaction to haptens mediated by skin-homing T cells, but the effector mechanisms responsible for the tissue damage are poorly understood. Here we studied the capacity of distinct subsets of hapten-specific T cells to induce apoptosis in autologous keratinocytes. Skin- and blood-derived nickel-specific CD8+ T cytotoxic 1 (Tc1) and Tc2 clones as well as CD4+ Th1 and Th2 expressed the cutaneous lymphocyte-associated Ag and exhibited strong MHC-restricted cytotoxicity against nickel-coupled B lymphoblasts, as detected by the [3H]TdR release assay. Both Tc1 and Tc2 clones, but not CD4+ T cells, displayed a significant cytotoxic activity against resting nickel-modified keratinocytes. Following IFN-gamma treatment, keratinocytes expressed MHC class II and ICAM-1 and became susceptible to Th1-mediated, but not Th2-mediated, cytotoxicity. The molecules of the two major cytotoxic pathways, Fas ligand (FasL) and perforin, were expressed by Tc1, Tc2, and Th1 cells, whereas Th2 cells expressed only FasL. Experiments performed in the presence of specific inhibitors of the perforin (concanamycin A) and FasL (brefeldin A) pathway indicated that perforin-mediated killing dominated in Tc1 and Tc2, and FasL-mediated cytotoxicity prevailed in Th2 clones, with a more heterogeneous behavior in the case of Th1 cells. Finally, perforin mRNA was expressed in ACD lesional skin, as assessed by RT-PCR analysis. In aggregate, our results indicate that keratinocytes can be target of multiple hapten-specific CTL responses, that may have distinct roles in the epidermal injury during ACD.

IL-4 enhances keratinocyte expression of CXCR3 agonistic chemokines

IFN-induced protein of 10 kDa (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha-chemoattractant (I-TAC) belong to the non-glutamate-leucine-arginine motif CXC chemokine family and act solely through the CXCR3 receptor for potent attraction of T lymphocytes. In this study, we evaluated the capacity of the T cell-derived cytokines IL-4, IL-10, and IL-17 to modulate IP-10, Mig, and I-TAC in cultured human keratinocytes and CXCR3 expression in T cells from allergic contact dermatitis (ACD). IL-4, but not IL-10 or IL-17, significantly up-regulated IFN-gamma- or TNF-alpha-induced IP-10, Mig, and I-TAC mRNA accumulation in keratinocytes and increased the levels of IP-10 and Mig in keratinocyte supernatants. Immunohistochemistry of skin affected by ACD revealed that >70% of infiltrating cells were reactive for CXCR3 and that CXCR3 staining colocalized in CD4+ and CD8+ T cells. Nickel-specific CD4+ and CD8+ T cell lines established from ACD skin produced IFN-gamma and IL-4 and expressed moderate to high levels of CXCR3. Finally, CXCR3 agonistic chemokines released by stimulated keratinocytes triggered calcium mobilization in skin-derived nickel-specific CD4+ T cells and promoted their migration, with supernatant from keratinocyte cultures stimulated with IFN-gamma and IL-4 attracting more efficaciously than supernatant from keratinocytes activated with IFN-gamma alone. In conclusion, IL-4 exerts a proinflammatory function on keratinocytes by potentiating IFN-gamma and TNF-alpha induction of IP-10, Mig, and I-TAC, which in turn may determine a prominent recruitment of CXCR3+ T lymphocytes at inflammatory reaction sites.

Epidermal cytokines in murine cutaneous irritant responses

Investigations on cytokines in skin irritancy or non-immunological irritant contact dermatitis (ICD) should improve our understanding of their complex mechanism. Numerous studies showed, however, that similar epidermal cytokines have been detected in irritant and allergic reactions, suggesting a lack of specific cytokines that clearly differentiate allergic from irritant reactions even though the pathomechanisms between allergic contact dermatitis (ACD) and ICD are distinguished. Recent data, however, indicate that some mediators may be restricted to allergic responses (contact hypersensitivity). This could provide the impetus to study their implication on irritant reactions. We overview the epidermal cytokines involved in irritant responses compared to those in contact hypersensitivity based on published results of studies using in vitro cell-cultured murine keratinocytes and in vivo murine models.

Expression of T-cell cytokines in challenged skin of murine allergic contact photosensitivity: low responsiveness is associated with induction of Th2 cytokines

Murine contact photosensitivity (CPS) to 3,3',4', 5-tetrachlorosalicylanilide (TCSA) is genetically controlled mainly by the major histocompatibility complex. The H-2(b,d) haplotypes are closely associated with high responders, whereas mice with H-2(k) are low or non-responders. We found that BALB/c (H-2(d)) mice were high responders in CPS not only to TCSA but also to chlorpromazine (CPZ) and benzocaine, whereas AKR/n (H-2(k)) mice were hyporesponsive to these three photoallergic agents. To elucidate the relationship between CPS responsiveness and T helper cell induction, the expression of T-cell cytokines was examined by reverse transcriptase polymerase chain reaction in the elicited skin of CPS to the three chemicals. The expression levels of interleukin(IL)-2 and interferon-gamma mRNAs were markedly higer in BALB/c mice than AKR/n mice, whereas mRNA for IL-4 was expressed strongly in AKR/n mice. These data suggest that the hyporesponsiveness of CPS to the photoallergens in AKR/n mice is closely associated with the activation/induction of Th2 cytokines at the challenged sites.

Effect of Am-80, a retinoid derivative, on 2, 4-dinitrofluorobenzene-induced contact dermatitis in mice

Retinoids have many pharmacological activities, including anti-inflammatory action and antiangiogenesis, effected through the regulation of various gene transcriptions. In this study, we investigated the effect of Am-80, one of the retinoic acid derivatives, on hapten-induced contact hypersensitivity in BALB/c mice. After application of 2,4-dinitrofluorobenzene (DNFB) to the ears of the mice, severe contact hypersensitivity with marked infiltration of inflammatory cells and hypertrophy of the epidermis was caused. The thickness of the ears increased biphasically and reached a peak 3 and 24 h after the DNFB challenge. Am-80 significantly inhibited ear thickness in the late-(24 h), but not the early-phase (3 h) reaction in a dose-dependent manner. In a histopathological study, obvious depression of edema and infiltration of inflammatory cells was observed in the ears of mice treated with Am-80. Am-80 inhibited the levels of expression in mice ears of interferon-gamma (IFN-gamma) and interleukin-6 (IL-6), but not tumor necrosis factor-alpha (TNF-alpha) or interleukin-4 (IL-4). Furthermore, Am-80 inhibited the antigen-induced production of some cytokines, including IFN-gamma and IL-6, but not IL-4, in vitro. Therefore, Am-80 inhibited hapten-induced contact hypersensitivity through the direct inhibition of inflammatory cytokines such as IFN-gamma and IL-6.

Signal transducer and activator of transcription 6 is essential in the induction of contact hypersensitivity

Contact hypersensitivity (CHS) is thought to be mainly associated with the activation of T helper type 1 (Th1) cells. However, there is also evidence that Th2 cells or Th2 cytokines play a role in the development of CHS. To analyze the functional contribution of Th2 cytokines interleukin (IL)-4 and IL-13, signal transducer and activator of transcription 6 (STAT6)-deficient (STAT6(-/)-) and wild-type (wt) control C57BL/6 mice were contact sensitized with 5% 2,4,6-trinitrochlorobenzene (TNCB), 0.5% 2,4-dinitrofluorobenzene, or 5% 4-ethoxyl methylene-2-phenyl-2-oxazolin-5-one, and any skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6(-/)- mice compared with wt mice.A histological analysis revealed that the infiltration of both eosinophils and neutrophils in the skin challenged after 24 h in STAT6(-/)- mice decreased substantially compared with that in wt mice. The expression of Th2 cytokines (IL-4, IL-5) in TNCB-challenged skin tissues and the supernatants from T cells stimulated by 2,4,6-trinitrobenzene sulfonate-modified spleen cells, as well as the immunoglobulin (Ig)E and IgG1 response after challenge, were also profoundly reduced in STAT6(-/)- mice, whereas the expression of interferon gamma was the same in STAT6(-/)- and wt mice after challenge. Furthermore, adoptive transfer experiments revealed that STAT6(-/)- mice induced CHS after injection of lymph node cells obtained from sensitized wt mice. Our data suggest that the STAT6 signal plays a critical role in the induction phase of CHS.

Profiles of cytokine mRNAs in the skin and lymph nodes of SENCAR mice treated epicutaneously with dibenzo[a,l]pyrene or dimethylbenz[a]anthracene reveal a direct correlation between carcinogen-induced contact hypersensitivity and epidermal hyperplasia

The potent carcinogenicity of dibenzo[a,l]pyrene (DB[a,l]P) in mouse skin is associated with an inflammatory response and a striking epidermal hyperplasia. The mechanism of these tissue responses is not known. However, a recent study has shown DB[a,l]P to be a contact sensitizer. In view of the programmed expression of cytokines during induction of contact hypersensitivity (CHS) and elicitation of CHS reactions, we analyzed cytokine mRNAs in treated skin and draining lymph nodes of SENCAR mice, at selected times after a single, epicutaneous application of DB[a,l]P or dimethylbenz[a]anthracene (DMBA), a substantially weaker carcinogen and a weaker contact sensitizer than DB[a,l]P. Cytokine mRNAs were quantified by first-strand DNA synthesis with reverse transcriptase (RT) and DNA amplification by the polymerase chain reaction (PCR). Histopathology of treated skin was determined in the same experiments. Time-response profiles of interferon (IFN) gamma and interleukin (IL) 2 in the DLN and IL1beta, IL10, tumor necrosis factor (TNF) alpha, and IL4 mRNAs in the skin of mice treated with 200 nmol of DB[a,l]P were in remarkable agreement with established profiles in mice treated with conventional contact sensitizers, e.g., oxazolone or dinitrochlorobenzene. Strong upregulation of DLN IFNgamma mRNA coupled with little change in IL 2 mRNA suggested a CD8(+) T-cell response characteristic of CHS induction. Coordinate expression of epidermal IL1beta, TNFalpha, and IL10 mRNAs, 24 h after DB[a,l]P treatment, was also characteristic of CHS induction. IL1beta and IL10 are upregulated by allergens and not by chemical irritants. Time-response profiles of epidermal IL1beta, TNFalpha, IL10, and IL4 mRNAs, 3-14 d after DB[a,l]P treatment, corresponded with expression of these cytokines during elicitation of CHS reactions. Epidermal IL4 is specifically upregulated during CHS reactions. Cytokine mRNA responses were dose-dependent (50, 100, and 200 nmol of DB[a,l]P) and markedly weaker in animals treated with 400 nmol of DMBA. Significantly, the intensity of epidermal hyperplasia correlated with the strength of the cytokine mRNA signals in DLN and skin. In conclusion, our data support carcinogen-specific CHS as a mechanism by which the very potent carcinogen DB[a,l]P induces epidermal hyperplasia, a requirement for tumor promotion in mouse skin.

Human CD4+ T lymphocytes with remarkable regulatory functions on dendritic cells and nickel-specific Th1 immune responses

The contribution of T helper (Th) and T cytotoxic (Tc) type 1 lymphocytes in the expression of allergic contact dermatitis to haptens has been amply documented. Conversely, the existence of T cell-based regulatory mechanisms has been poorly investigated. Here, we examined the properties of a subset of nickel-specific CD4+ T cells displaying the cytokine profile (IL-10 , IL-5 , IFN-gamma+/-, IL-4+/-) of T regulatory cells 1 (Tr1) and with the potential to down-modulate immune responses to nickel. Tr1 clones were isolated from skin challenged with NiSO4 and peripheral blood of nickel-allergic patients, and from the blood of healthy individuals. Tr1 clones expressed CD25, CD28, CD30, CD26, and the IL-12 receptor beta2 chain upon activation, whereas the lymphocyte activation antigen-3 was present on 50% of the clones. Monocytes precultured with Tr1 cells in the presence of nickel, or treated with Tr1-derived supernatant, exhibited a markedly diminished capacity to stimulate nickel-specific Th1 responses. Tr1 supernatants also blocked the differentiation of dendritic cells (DC) from monocytes, as well as DC maturation and IL-12 production induced by lipopolysaccharide. As a consequence, the ability of DC to stimulate nickel-specific Th1 and Tc1 responses was greatly impaired. These inhibitory effects were completely prevented by IL-10, but not IL-5, neutralization. In aggregate, the results indicate that Tr1 cells can potently regulate the expression of Th1-mediated allergic diseases via release of IL-10.

Induction of 3beta-hydroxysteroid dehydrogenase/isomerase type 1 expression by interleukin-4 in human normal prostate epithelial cells, immortalized keratinocytes, colon, and cervix cancer cell lines

The 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) isoenzymes catalyze an essential step in the formation of all classes of active steroid hormones. In humans there are two 3beta-HSD isoenzymes, the type 1 gene being predominantly expressed in the placenta and peripheral tissues, whereas the type 2 gene is the predominant 3beta-HSD expressed in the adrenal glands and gonads. We have recently showed that interleukin (IL)-4 and IL-13 induce 3beta-HSD type 1 gene expression in human breast cancer cell lines as well as in normal human mammary epithelial cells. The present study was designed to investigate whether such a cytokine-induced 3beta-HSD type 1 expression would also be observed in cell types derived from other peripheral sex steroid target tissues. To gain further knowledge about the molecular mechanism of IL-4 action, we have studied whether the induction of 3beta-HSD type 1 expression in IL-4-responsive cell types would always be associated with the activation of Stat6, a member of the Signal Transducers and Activators of Transcription (STAT) gene family. Stat6 is recognized as the principal transcription factor mediating the effects of IL-4. In normal human prostate epithelial cells (PrEC), no 3beta-HSD activity was detectable under basal culture conditions, while exposure to IL-4 or IL-13 caused a potent induction of this activity. This effect results from a rapid induction of 3beta-HSD type 1 messenger RNA levels as determined by Northern blot and RT-PCR analyses. Furthermore, IL-4 and IL-13 also increased 3beta-HSD type 1 gene expression in human HaCaT immortalized keratinocytes, ME-180 cervix cancer cells, HT-29 colon cancer cells as well as in BT-20 and ZR-75-1 breast cancer cells. However, IL-4 and IL-13 failed to modulate the 3beta-HSD type 1 expression in human LnCAP and PC-3 prostate cancer cells, Caco-2 colon cancer cells as well as in JAR and JEG-3 choriocarcinoma cell lines. The DNA-binding activity of Stat6 was activated after a 30-min exposure to IL-4 in PrEC and in all the cell types where IL-4 induced 3beta-HSD expression, but not in those that failed to respond to IL-4. Our data therefore suggest that IL-4 and IL-13 may play a role in the biosynthesis of active sex steroids from the inactive adrenal steroid dehydroepiandrosterone, not only in breast cells but also in various cell types derived from peripheral target tissues, such as normal human prostate epithelial cells, immortalized keratinocytes, as well as colon and cervix cancer cell lines. Our data also demonstrates that the stimulatory effect of IL-4 was always associated with the activation of Stat6, thus supporting the essential role of Stat6 in this induction of 3beta-HSD type 1 gene expression.

IL-4 inhibits the migration of human Langerhans cells through the downregulation of TNF receptor II expression

The migration of Langerhans cells is an initial event in the sensitization phase of contact sensitivity. Langerhans cells travel from the epidermis to the regional lymph node, and can be variously modulated in the skin where many cytokines are released from epidermal cells, dermal cells, T helper (Th) cells, and other inflammatory cells during the sensitization and elicitation phase of contact dermatitis, and thus induce an altered inflammatory skin reaction. The modulatory effect of the cytokines released in the skin, such as IL-1beta, GM-CSF, and TNF-alpha as epidermal cytokines, IL-2, IL-12, and IFN-gamma as Th1 type cytokines, and IL-4 and IL-10 as Th2 type cytokines, was analyzed using the chemotactic chamber method in this study. Both GM-CSF and TNF-alpha induced the migration of human Langerhans cells in vitro, whereas IL-1beta, IL-2, IL-10, IL-12, and IFN-gamma had no effect on Langerhans cell migration. In contrast, IL-4 inhibited Langerhans cell migration in a dose dependent manner. The inhibitory activity of IL-4 was reversed by both anti-human IL-4 monoclonal antibody and anti-human IL-4 receptor monoclonal antibody. IL-4 inhibited the Langerhans cell migration induced by both TNF-alpha and GM-CSF. Furthermore, anti-TNF-RII monoclonal antibody inhibited both random migration and the migration induced by TNF-alpha, but not that induced by GM-CSF. A reverse-transcriptase-polymerase chain reaction and fluorescence-activated cell sorter analysis revealed that TNF-alpha up-regulated and IL-4 downregulated the TNF receptor II (TNF-RII) expression of Langerhans cells at both the mRNA and the protein levels. The pretreatment of Langerhans cells with TNF-alpha enhanced the migration of Langerhans cells and the expression of TNF-RII. After pretreating Langerhans cells with TNF-alpha, IL-4 inhibited both the migration of Langerhans cells and the expression of TNF-RII in a time dependent manner. These results indicate that IL-4 inhibits the migratory activity of Langerhans cells by downregulating the expression of TNF-RII in human Langerhans cells and thereby modulates the immune response in the skin.

Distinct In Vivo and In Vitro Cytokine Profiles of Draining Lymph Node Cells in Acute and Chronic Phases of Contact Hypersensitivity: Importance of a Type 2 Cytokine-Rich Cutaneous Milieu for the Development of an Early-Type Response in the Chronic Phase

Although regional lymph nodes (LN) have been extensively studied as rich sources of effector T cells in contact hypersensitivity (CH), it remains unknown whether T cell responses in the LN reflect those in effector skin sites. We previously showed that repeated elicitation of CH results in a shift in the time course of Ag-specific CH from a delayed-type hypersensitivity response to an early-type response, a reflection of a shift in cutaneous cytokine expression from a type 1 to a type 2 profile. To investigate whether repeated elicitation of CH could also drive T cell development to the type 2 phenotype in the regional draining LN, sequential cytokine gene expression after hapten application was assessed during both the acute and the chronic phase of CH. In the draining LN the shift to type 2 cytokine production was also observed, but more mixed patterns of responses were induced than in the corresponding skin sites. The chronic LN cells (LNC), when stimulated in vitro, produced markedly lower levels of type 1 cytokines and higher levels of type 2 cytokines than the acute LNC. A successful passive transfer of an early-type response by the LNC was only induced in the recipient mice when the skin sites chronically treated with hapten were elicited. These results indicate that an early-type response by regional LNC would take place only in a milieu with sufficient levels of type 2 cytokines.

Inhibition of allergic contact dermatitis to DNCB but not to oxazolone in interleukin-4-deficient mice

The role of interleukin-4 as a regulator of immune responses in the skin is investigated with regard to the outcome of contact hypersensitivity reaction in interleukin-4-deficient BALB/C mice. In previous studies conflicting results were obtained concerning the role of interleukin-4 in contact hypersensitivity reactions supporting either a proinflammatory or rather an inhibitory function of this cytokine. Interleukin-4 deficient BALB/C mice sensitized to 2,4-dinitrochlorobenzene showed after challenge a significant reduction in magnitude and duration of the contact hypersensitivity response in comparison with wild-type mice. This attenuation was accompanied by a significant reduction of edema and cellular infiltrates in the dermis and a lacking induction of IL-10 mRNA expression in skin. Also, adoptive transfer experiments revealed that BALB/C mice failed to exhibit contact hypersensitivity after injection of lymph node cells obtained from sensitized interleukin-4 deficient mice. To examine further the role of the contact allergen used to induce the contact hypersensitivity response, mice were also sensitized and challenged with Oxazolone. Here a similar magnitude and duration of contact hypersensitivity in both the interleukin-4 deficient mice and BALB/C control mice was observed. This indicates that the contact hypersensitivity response to 2,4-dinitrochlorobenzene and Oxazolone may partly evolve on different pathways being dependent and independent of interleukin-4. Our results clearly show that the complete loss of endogenous interleukin-4 expression in BALB/C mice is associated with an impaired manifestation of contact hypersensitivity response to 2,4-dinitrochlorobenzene, implying an important proinflammatory function of this cytokine.

Cytotoxicity is mandatory for CD8(+) T cell-mediated contact hypersensitivity

Contact hypersensitivity (CHS) is a T cell-mediated skin inflammation induced by epicutaneous exposure to haptens in sensitized individuals. We have previously reported that CHS to dinitrofluorobenzene in mice is mediated by major histocompatibility complex (MHC) class I-restricted CD8(+) T cells. In this study, we show that CD8(+) T cells mediate the skin inflammation through their cytotoxic activity. The contribution of specific cytotoxic T lymphocytes (CTLs) to the CHS reaction was examined both in vivo and in vitro, using mice deficient in perforin and/or Fas/Fas ligand (FasL) pathways involved in cytotoxicity. Mice double deficient in perforin and FasL were able to develop hapten-specific CD8(+) T cells in the lymphoid organs but did not show CHS reaction. However, they did not generate hapten-specific CTLs, demonstrating that the CHS reaction is dependent on cytotoxic activity. In contrast, Fas-deficient lpr mice, FasL-deficient gld mice, and perforin-deficient mice developed a normal CHS reaction and were able to generate hapten-specific CTLs, suggesting that CHS requires either the Fas/FasL or the perforin pathway. This was confirmed by in vitro studies showing that the hapten-specific CTL activity was exclusively mediated by MHC class I-restricted CD8(+) T cells which could use either the perforin or the Fas/FasL pathway for their lytic activity. Thus, cytotoxic CD8(+) T cells, commonly implicated in the host defence against tumors and viral infections, could also mediate harmful delayed-type hypersensitivity reactions.

Epicutaneous administration of hapten through patch application augments TH2 responses which can downregulate the elicitation of murine contact hypersensitivity

BACKGROUND AND OBJECTIVE

Allergic contact dermatitis and its animal model, contact hypersensitivity (CHS), have long been documented as type 1 T-cell-predominant immune responses. Although type 1/type 2 T-cell deviation has been repeatedly demonstrated to play an important role in many human diseases and their animal models, the potential of tilting type 1/type 2 T-cell differentiation of CHS by modulating the manner of administration and dosage of hapten remains unexplored. This study examined the effect of these two factors on type 1/type 2 balance of CHS.

METHODS

ELISA methods for detection of isotypes of hapten-specific antibodies and cytokine profiles of in vitro reactivation culture as well as ear-swelling assay were used to indicate type 1 or type 2 T-cell immune responses.

RESULTS

In this paper, it was demonstrated that dosage of hapten has no effect on the type 1/ type 2 T-cell balance of CHS, whereas epicutaneous administration of hapten through patch application could tilt the type 1/type 2 balance to decrease type 1 and to augment type 2 T-cell responses. Patch application-induced modulation is still effective in ever-sensitized mice and the augmented type 2 T-cell responses are persistent and increase progressively in strength after repeated immunizations. Moreover, it was demonstrated that the augmented type 2 T-cell response can downregulate the elicitation of CHS. The major mediating cells of the enhanced type 2 T-cell responses were determined to be CD4+ T cells (TH2 cells).

CONCLUSIONS

These data show that epicutaneous administration of hapten through patch application augments TH2 response which can downregulate the elicitation of murine CHS. This exploration may contribute to the understanding of regulatory mechanisms involved in contact allergy.