The expression of Th1 and Th2 type cytokines in a lesion of allergic contact dermatitis

Review of biologics in allergic contact dermatitis

The resistant and recalcitrant nature of severe allergic contact dermatitis (ACD) makes its management challenging. With advances in the understanding of the cellular and molecular pathogenesis of ACD, newer therapeutic targets are becoming apparent. In particular, the use of biologics has gained momentum, given the specificity of their action. This article aims to review the presently available data on the use of biologics in ACD. English-language-based literature available on the use of biological therapy was thoroughly probed in the following databases as on October 14, 2019: PubMed, Google Scholar, The Cochrane library, Embase, Scopus, and EBSCO. The following keywords were used: "contact dermatitis", "allergens", "delayed-type hypersensitivity reaction", "biologics", "biological therapy", "monoclonal antibodies", "patch testing", "TNF-α inhibitors", "infliximab", "adalimumab", "etanercept", "dupilumab", "omalizumab", "secukinumab", "ustekinumab", "rituximab".

Calcitonin gene-related peptide is an important regulator of cutaneous immunity: effect on dendritic cell and T cell functions

Some cutaneous inflammations are induced by percutaneous exposure to foreign Ags, and many chemical mediators regulate this inflammation process. One of these mediators, calcitonin gene-related peptide (CGRP), is a neuropeptide released from nerve endings in the skin. CGRP binds to its receptors composed of receptor activity-modifying protein 1 and calcitonin receptor-like receptor to modulate immune cell function. We show that CGRP regulates skin inflammation under physiological conditions, using contact hypersensitivity (CHS) models of receptor activity-modifying protein 1-deficient mice. CGRP has different functions in CHS responses mediated by Th1 or Th2 cells; it inhibits Th1-type CHS, such as 2,4,6-trinitrochlorobenzene-induced CHS, but promotes Th2-type CHS, such as FITC-induced CHS. CGRP inhibits the migration of Langerin(+) dermal dendritic cells to the lymph nodes in 2,4,6-trinitrochlorobenzene-induced CHS, and upregulates IL-4 production of T cells in the draining lymph nodes in FITC-CHS. These findings suggest that CGRP regulates several types of CHS reactions under physiological conditions and plays an important role in cutaneous immunity.

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.

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.

Interleukin-12 enhances contact hypersensitivity by modulating the in vivo cytokine pattern in mice

It has been proven that interleukin-12 (IL-12) can modify Th1 and Th2 cell-mediated immune diseases by altering the development and cytokine production of the cells. In this study, we investigated the in vivo immunomodulatory effect of recombinant murine IL-12 on contact hypersensitivity, a Th1 cell-mediated disease. For this purpose, Balb/C mice were sensitized with 3% 4-ethyoxymethylene-2-phenyl-oxazol-5-one (OXAZ), and recombinant mouse IL-12 was given simultaneously during the induction phase. Contact allergy was then elicited by ear challenge with 1% OXAZ. We examined the mouse ear swelling response, in vivo cytokine gene expression in the skin and local lymph nodes, and in vitro cytokine production by the spleen lymphocytes. It was found that in vivo IL-12 treatment during the induction phase significantly enhanced the ear swelling response to OXAZ in sensitized mice. Moreover, remarkable mononuclear cell infiltration and edema and higher expression of Th1 cytokine mRNAs (IL-2 and interferon-gamma) in the skin lesion and local lymph nodes were observed in contact allergic mice with IL-12 treatment compared with contact allergic mice without IL-12 treatment. The expression of Th2 cytokine mRNA (IL-4) in the skin lesion and local lymph nodes, however, was largely downregulated, with no change in IL-5 mRNA in IL-12-treated contact allergic mice. We found, unexpectedly, that, similar to the effects on phytohemagglutinin (PHA) stimulated in vitro IL-2 and IFN-gamma production, PHA-induced in vitro IL-4 production was enhanced in the spleen lymphocytes from IL-12-treated contact allergic mice. Our results indicate that exogenous IL-12 enhanced contact hypersensitivity probably because of the in vivo promoting and suppressing effects of IL-12 on Th1 and Th2 gene expression, respectively.