Miwa Kobayashi

Possible Pathogenic Role of Th17 Cells for Atopic Dermatitis

The critical role of IL-17 has recently been reported in a variety of conditions. Since IL-17 deeply participates in the pathogenesis of psoriasis and keratinocyte production of certain cytokines, the involvement of T helper cell 17 (Th17) in atopic dermatitis (AD) is an issue to be elucidated. To evaluate the participation of Th17 cells in AD, we successfully detected circulating lymphocytes intracellularly positive for IL-17 by flow cytometry, and the IL-17+ cell population was found exclusively in CD3+CD4+ T cells. The percentage of Th17 cells was increased in peripheral blood of AD patients and associated with severity of AD. There was a significant correlation between the percentages of IL-17+ and IFN-gamma+ cells, although percentage of Th17 cells was not closely related to Th1/Th2 balance. Immunohistochemically, IL-17+ cells infiltrated in the papillary dermis of atopic eczema more markedly in the acute than chronic lesions. Finally, IL-17 stimulated keratinocytes to produce GM-CSF, TNF-alpha, IL-8, CXCL10, and VEGF. A marked synergistic effect between IL-17 and IL-22 was observed on IL-8 production. The number of Th17 cells is increased in the peripheral blood and acute lesional skin of AD. Th17 cells may exaggerate atopic eczema.

Innate immunity mediated by epidermal keratinocytes promotes acquired immunity involving Langerhans cells and T cells in the skin

Skin is an immunological organ consisting of epidermal cells, i.e. keratinocytes and Langerhans cells (LCs, antigen‐presenting dendritic cells), and both innate and acquired immune systems operate upon exposure of the skin to various external microbes or their elements. To explore the relationship between innate and acquired immunities in the skin, we investigated whether Toll‐like receptor (TLR) ligation of epidermal cells enhances the ability of LCs to present a specific antigen to T cells in mice. LC‐containing epidermal cells were incubated with CpG oligonucleotide (TLR9 ligand) modified with trinitrophenyl hapten, and cultured with hapten‐primed CD4+ T cells. TLR9 ligand was capable of enhancing the hapten‐presenting ability of LCs when LC‐enriched epidermal cells, but not purified LCs, were used as the LC source, suggesting that bystander keratinocytes play a role in the enhancement of LC function. Cultivation of freshly isolated epidermal cells with CpG promoted the expression of major histocompatibility complex (MHC) class II and CD86 molecules on LCs. CpG enhanced the production of interleukin (IL)‐1α, granulocyte–macrophage colony‐stimulating factor (GM‐CSF) and tumour necrosis factor (TNF)‐α by primarily cultured keratinocytes. The addition of a cocktail of neutralizing antibodies against these cytokines abrogated the CpG‐promoted, antigen‐presenting ability of LC‐enriched epidermal cells. Moreover, the addition of culture supernatants from CpG‐stimulated keratinocytes restored the ability of purified LCs. Our study demonstrated that although the direct effect of CpG on LCs is minimal, LC function can be up‐regulated indirectly by cytokines released by CpG‐stimulated keratinocytes. This also implies that innate immunity evoked by TLR ligation of keratinocytes enhances acquired immunity comprising LCs and T cells.

Type of skin eruption is an independent prognostic indicator for adult T-cell leukemia/lymphoma

Cutaneous involvement is seen in ~ 50% of adult T-cell leukemia/lymphoma (ATLL) patients. We investigated the association between skin eruption type and prognosis in 119 ATLL patients. ATLL eruptions were categorized into patch (6.7%), plaque (26.9%), multipapular (19.3%), nodulotumoral (38.7%), erythrodermic (4.2%), and purpuric (4.2%) types. When the T stage of the tumor-node-metastasis-blood (TNMB) classification of mycosis fungoides/Sézary syndrome was applied to ATLL staging, 16.0% were T1, 17.7% T2, 38.7% T3, and 4.2% T4, and the remaining 23.5% were of the multipapular and purpuric types. For the patch type, the mean survival time (median survival time could not be estimated) was 188.4 months. The median survival times (in months) for the remaining types were as follows: plaque, 114.9; multipapular, 17.3; nodulotumoral, 17.3; erythrodermic, 3.0; and purpuric, 4.4. Kaplan-Meier curves of overall survival showed that the erythrodermic type had the poorest prognosis, followed by the nodulotumoral and multipapular types. The patch and plaque types were associated with better survival rates. Multivariate analysis demonstrated that the hazard ratios of the erythrodermic and nodulotumoral types were significantly higher than that of the patch type, and that the eruption type is an independent prognostic factor for ATLL. The overall survival was worse as the T stage became more advanced: the multipapular type and T2 were comparable, and the purpuric type had a significantly poorer prognosis than T1.

Expression of toll-like receptor 2, NOD2 and dectin-1 and stimulatory effects of their ligands and histamine in normal human keratinocytes

Background  Epidermal keratinocytes are involved in the skin innate immunity and express toll‐like receptors (TLRs) and other innate immune proteins. The epidermis is continuously exposed to pathogenic Gram‐positive bacteria or fungi. However, few studies have examined the function and expression of innate immune proteins in keratinocytes. Histamine, which is well known for itch and allergy, is closely associated with innate immunity, but its influence on epidermal innate immunity is still unclear.

A group of atopic dermatitis without IgE elevation or barrier impairment shows a high Th1 frequency: possible immunological state of the intrinsic type.

BACKGROUND Atopic dermatitis (AD) can be classified into the major extrinsic type with high serum IgE levels and impaired barrier, and the minor intrinsic type with normal IgE levels and unimpaired barrier. OBJECTIVE To characterize the intrinsic type of Japanese AD patients in the T helper cell polarization in relation to the barrier condition. METHODS Enrolled in this study were 21 AD patients with IgE<200kU/L (IgE-low group; 82.5±59.6kU/L) having unimpaired barrier, and 48 AD patients with IgE>500kU/L (IgE-high group; 8.050±10.400kU/L). We investigated filaggrin gene (FLG) mutations evaluated in the eight loci common to Japanese patients, circulating Th1, Th2 and Th17 cells by intracellular cytokine staining and flow cytometry, and blood levels of CCL17/TARC, IL-18, and substance P by ELISA. RESULTS The incidence of FLG mutations was significantly lower in the IgE-low group (10.5%) than the IgE-high group (44.4%) (normal individuals, 3.7%). The percentage of IFN-γ-producing Th1, but not Th2 or Th17, was significantly higher in the IgE-low than IgE-high group. Accordingly, Th2-attracting chemokine CCL17/TARC, was significantly lower in the IgE-low than the IgE-high group. There were no differences between them in serum IL-18 levels, or the plasma substance P levels or its correlation with pruritus. CONCLUSION The IgE-low group differed from the IgE-high group in that it had much less FLG mutations, increased frequency of Th1 cells, and lower levels of CCL17. In the intrinsic type, non-protein antigens capable of penetrating the unimpaired barrier may induce a Th1 eczematous response.

Cutaneous Hypersensitivities to Hapten Are Controlled by IFN-γ-Upregulated Keratinocyte Th1 Chemokines and IFN-γ-Downregulated Langerhans Cell Th2 Chemokines

There are immediate, late-phase, and delayed-type reactions to exogenous agents. In IFN-gamma-knockout (IFN-gamma(-/-)) and wild-type B6 mice, we examined the response to picryl chloride (PCl) for assessing delayed-type reactions, and the responses to repeatedly challenged FITC for immediate and late-phase reactions. The delayed-type hypersensitivity was depressed in IFN-gamma(-/-) mice, and the immediate and late-phase reactions were enhanced in IFN-gamma(-/-) mice. As skin-infiltrating lymphocytes were scarce at the PCl-challenged site of IFN-gamma(-/-) mice, we investigated chemokine production by keratinocytes and Langerhans cells (LCs). A real-time PCR analysis demonstrated that Th1 chemokines (CXCL9 and CXCL10) and Th2 chemokines (CCL17 and CCL22) were derived mainly from keratinocytes and LCs, respectively. Challenge with PCl or FITC augmented keratinocyte expression of Th1 chemokines in wild-type but not in IFN-gamma(-/-) mice, and Th2 chemokine production by LCs was induced by repeated FITC in IFN-gamma(-/-) mice. Finally, transfer of carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled draining lymph node cells from hapten-sensitized B6 mice or lymph node cells from sensitized green fluorescent protein (GFP) mice to naive IFN-gamma(-/-) mice revealed less infiltration of CFSE(+) or GFP(+) lymphocytes at the challenged site. Our study suggests that one of the crucial actions of IFN-gamma is upregulation of keratinocyte production of Th1 chemokines and downregulation of LC production of Th2 chemokines.

Induction of eosinophil- and Th2-attracting epidermal chemokines and cutaneous late-phase reaction in tape-stripped skin

Abstract:  Skin barrier damage induces various harmful or even protective reactions in the skin, as represented by enhancement of keratinocyte cytokine production. To investigate whether acute removal of stratum corneum modulates the production of chemokines by epidermal cells, we treated ears of BALB/c and C57BL/6 mice by tape‐stripping, or acetone‐rubbing as a control of acute barrier disruption procedure. There was no difference between the tape‐stripped and acetone‐rubbed skin sites in the increased and recovered levels of transepidermal water loss. The mRNA expression levels of all the chemokines tested, including Th1 chemokines (CXCL10, CXCL9 and CXCL11), Th2 chemokines (CCL17 and CCL22) and eosinophil chemoattractant (CCL5), were higher in the epidermal cells from BALB/c than in those of C57BL/6 mice. In particular, CCL17, CCL22 and CCL5 were remarkably elevated in BALB/c mice and augmented by tape‐stripping more markedly than acetone‐rubbing, whereas Th1 chemokines were enhanced by acetone‐rubbing more remarkably. Tape‐stripping induced dermal infiltration of eosinophils in BALB/c but not C57BL/6 mice. In a contact hypersensitivity model, where BALB/c mice were sensitized on the abdomen and challenged on the ears with fluorescein isothiocyanate, mice exhibited higher ear swelling responses at the late‐phase as well as delayed‐type reactions, when challenged via the tape‐stripped skin. The challenge via tape‐stripped skin augmented the expression of IL‐4 and CCR4 in the skin homogenated samples, indicating infiltration of Th2 cells. These findings suggest that acute barrier removal induces the expression of Th2 and eosinophil chemokines by epidermal cells and easily evokes the late phase reaction upon challenge with antigen.

Comparison of skin barrier function and sensory nerve electric current perception threshold between IgE‐high extrinsic and IgE‐normal intrinsic types of atopic dermatitis

Background  Two types of atopic dermatitis (AD) have been proposed, with different pathophysiological mechanisms underlying this seemingly heterogeneous disorder. The extrinsic type shows high IgE levels presumably as a consequence of skin barrier damage and feasible allergen permeation, whereas the intrinsic type exhibits normal IgE levels and is not mediated by allergen‐specific IgE.

Aberrant aquaporin 5 expression in the sweat gland in aquagenic wrinkling of the palms

Aquagenic wrinkling of the palms (AWP) is an uncommon disease characterized by the rapid and transient formation of edematous whitish plaques on the palms on exposure to water. Although this disease is occasionally accompanied by hyperhidrosis, the pathophysiology of AWP remains unknown. Herein we describe a patient with AWP. The location of wrinkling was limited to the areas positive for iodine-starch test after water exposure, which suggests that AWP is etiologically related to hyperhidrosis. Histologic examination revealed hyperplastic and papillated eccrine glandular epithelium with the enlarged diameter of eccrine coils. Immunohistochemically, while aquaporin 5 (AQP5), one of the water channel AQP families, was present exclusively in the dark cells of sweat glands of healthy donors, an aberrant AQP5 staining, extending to the clear cells, was found in the patient with AWP. The hyperplastic glandular epithelium and aberrant AQP5 staining in the patients sweat glands suggest that AWP stems from dysregulation of sweating.

Epidermal chemokines and modulation by antihistamines, antibiotics and antifungals

Abstract: Growing evidence has demonstrated that chemokines released from epidermal cells control inflammatory skin diseases. Keratinocytes elaborate both Th1‐ and Th2‐associated chemokines, although the former is more abundantly produced than the latter. Downmodulation of keratinocyte production of chemokines is one of the therapeutic approaches for cutaneous inflammatory disorders. Recent observations have shown that keratinocyte chemokine production can be modulated by well‐used drugs, including antihistamines, antibiotics and antifungals. Utilization of the beneficial side effects of these drugs may by clinically valuable.