Tatsuo Yudate

Dectin-2 is a pattern recognition receptor for fungi that couples with the Fc receptor γ chain to induce innate immune responses

Antigen presenting cells recognize pathogens via pattern recognition receptors (PRR), which upon ligation transduce intracellular signals that can induce innate immune responses. Because some C-type lectin-like receptors (e.g. dectin-1 and DCSIGN) were shown to act as PRR for particular microbes, we considered a similar role for dectin-2. Binding assays using soluble dectin-2 receptors showed the extracellular domain to bind preferentially to hyphal (rather than yeast/conidial) components of Candida albicans, Microsporum audouinii, and Trichophyton rubrum. Selective binding for hyphae was also observed using RAW macrophages expressing dectin-2, the ligation of which by hyphae or cross-linking with dectin-2-specific antibody led to protein tyrosine phosphorylation. Because dectin-2 lacks an intracellular signaling motif, we searched for a signal adaptor that permits it to transduce intracellular signals. First, we found that the Fc receptor γ (FcRγ) chain can bind to dectin-2. Second, ligation of dectin-2 on RAW cells induced tyrosine phosphorylation of FcRγ, activation of NF-κB, internalization of a surrogate ligand, and up-regulated secretion of tumor necrosis factor α and interleukin-1 receptor antagonist. Finally, these dectin-2-induced events were blocked by PP2, an inhibitor of Src kinases that are mediators for FcRγ chain-dependent signaling. We conclude that dectin-2 is a PRR for fungi that employs signaling through FcRγ to induce innate immune responses.

Expression of NF-κB in epidermis and the relationship between NF-κB activation and inhibition of keratinocyte growth

Summary Background Nuclear factor‐κB (NF‐κB) is a transcription factor involved in a number of signalling pathways in many cell types. NF‐κB in mice has been implicated as an important regulator of keratinocyte proliferation and differentiation.

RANTES mRNA Expression in Skin and Colon of Patients with Atopic Dermatitis

The expression of RANTES mRNA in dermal and colonic tissue was examined in patients with atopic dermatitis by the reverse transcription polymerase chain reaction method. RANTES mRNA was detected in the colon in 8 of 10 patients and in 1 of 5 control patients. It was present in rashes in 9 of 10 patients and at non-eruptive sites in 5 of 7 patients. These findings suggest that RANTES is involved in eosinophil infiltration and T cell infiltration in atopic dermatitis.

Enhanced production of RANTES, an eosinophil chemoattractant factor, by cytokine-stimulated epidermal keratinocytes.

In allergic skin diseases such as atopic dermatitis (AD), eosinophils migrate from the circulation to the skin. We investigated the mechanisms of eosinophil chemotaxis in atopic dermatitis by examining the effect of stimulation of epidermal keratinocytes (KC) by inflammatory cytokines, interferon-gamma (IFNgamma) and/or tumor necrosis factor-alpha (TNF alpha) on the production of eosinophil chemotactic factors. Simultaneous addition of IFNgamma and TNF alpha to culture KC synergistically increased eosinophil chemotaxis and the expression of RANTES mRNA and protein level on these cells. Anti-RANTES antibody blocked eosinophil chemotaxis by IFNgamma- and TNF alpha-stimulated KC. Our results indicate that the production of RANTES by KC may help to explain eosinophil infiltration into the skin in AD.

Binding of DC-HIL to dermatophytic fungi induces tyrosine phosphorylation and potentiates antigen presenting cell function.

APCs express receptors recognizing microbes and regulating immune responses by binding to corresponding ligands on immune cells. Having discovered a novel inhibitory pathway triggered by ligation of DC-HIL on APC to a heparin/heparan sulfate-like saccharide of syndecan-4 on activated T cells, we posited DC-HIL can recognize microbial pathogens in a similar manner. We showed soluble recombinant DC-HIL to bind the dermatophytes Trichophyton rubrum and Microsporum audouinii, but not several bacteria nor Candida albicans. Dermatophyte binding was inhibited completely by the addition of heparin. Because DC-HIL contains an ITAM-like intracellular sequence, we questioned whether its binding to dermatophytes can induce tyrosine phosphorylation in dendritic cells (DC). Culturing DC with T. rubrum (but not with C. albicans pseudohyphae) induced phosphorylation of DC-HIL, but not when the tyrosine residue of the ITAM-like sequence was mutated to phenylalanine. To examine the functional significance of such signaling on DC, we cross-linked DC-HIL with mAb (surrogate ligand), which not only induced tyrosine phosphorylation but also up-regulated expression of 23 genes among 662 genes analyzed by gene-array, including genes for profilin-1, myristoylated alanine rich protein kinase C substrate like-1, C/EBP, LOX-1, IL-1β, and TNF-α. This cross-linking also up-regulated expression of the activation markers CD80/CD86 and heightened APC capacity of DC to activate syngeneic T cells. Our findings support a dual role for DC-HIL: inhibition of adaptive immunity following ligation of syndecan-4 on activated T cells and induction of innate immunity against dermatophytic fungi.

Role of staphylococcal enterotoxins in pathogenesis of atopic dermatitis: growth and expression of T cell receptor Vβ of peripheral blood mononuclear cells stimulated by enterotoxins A and B

In order to investigate the role of staphylococcal enterotoxins in the pathogenesis of dermatitis in atopic patients, the growth and expression of T cell receptor V beta in peripheral blood mononuclear cells (PBMCs) from atopic dermatitis patients induced by stimulation with staphylococcal enterotoxin A (SEA) or staphylococcal enterotoxin B (SEB) were examined. Lymphocyte stimulation tests (LST) using SEA or SEB were performed in atopic dermatitis (AD) patients (n = 10) and normal controls (n = 5). PBMCs from AD patients displayed significantly stronger responses to SEA or SEB than those from the controls. To ascertain further whether SEA acts as a superantigen in atopic dermatitis, the expression of 22 genes in the variable region of the beta chain (V beta) of T cell receptors (TcR) was examined before and after stimulation with SEA by a reverse transcriptase-polymerase chain reaction (RT-PCR). Before stimulation, only weak expression of V beta was observed, and the expression of the various V beta segments was uniform in the normal controls (n = 3). In the AD patients (n = 3), the expression of V beta was enhanced, but was not uniform in 2 out of 3 patients and the pattern of expression was characteristic in each individual. This suggests that V beta expression varies in individual AD patients and displays restricted heterogeneity, reflecting the diversity of the etiology of the disease. After culture of the SEA-stimulated cells, no difference was observed in the expression of TcR V beta segments in the 3 normal controls as compared with that prior to stimulation, but particular V beta segments were intensely expressed in 3 AD patients, displaying distinct patterns (case I: V beta 9, V beta 10, V beta 18; case 2: V beta 6.1-3; case 3: V beta 6.1-3, V beta 18). Many of these V beta segments corresponded with those known to be induced by SEA. These results suggest oligoclonal proliferation of T cells in the peripheral blood of AD patients and high responsiveness in each clone, and since the expression of V beta segment after SEA stimulation was restricted, the actions of staphylococcal enterotoxins as superantigens were suggested.

Epinastine Inhibits Eosinophil Chemotaxis and Adhesion Molecules in Atopic Dermatitis

Purpose: To investigate the effects of epinastine on eosinophil chemotaxis and changes in eosinophil adhesion molecules induced by epinastine and three other antiallergic agents, using eosinophils of atopic dermatitis (AD) patients. Results: Epinastine reduced eosinophil chemotaxis toward eotaxin when the eosinophils had been prestimulated with interleukin (IL)-5, but given alone it did not alter eosinophil chemotaxis toward IL-5. CD11b expression was inhibited when peripheral blood was prestimulated with IL-5, but eosinophil adhesion molecule expression was not altered. Conclusions: Epinastine suppresses allergic inflammation not only through its strong antihistamine and antimediator effects, but also by inhibiting eosinophilic chemotaxis and the expression of adhesion molecules involved in chemotaxis, especially CD11b.

Overexpression of CD11b on Eosinophils in Atopic Dermatitis: Downregulation by Cyclosporin A and Upregulation by Interleukin 5

We examined the level of expression of CD11b on eosinophils in pripheral blood samples from patients with atopic dermatitis (AD) and non-AD volunteers. Eosinophils were defined using a new method employing CD14/CD45 and a backgate technique. Overexpression of CD11b was noted in eosinophils of AD patients. Treatment of AD with cyclosporin A resulted in clinical improvement as well as reduction in the expression of CD11b. Stimulation of eosinophils from patients with inactive AD by interleukin 5 upregulated the expression of CD11b on these cells. Our results suggest that the expression of CD11b surface molecule on eosinophils may play an important role in the activity of AD.

Tinea barbae due to Trichophyton rubrum with possible involvement of autoinoculation.

q 2000 British Association of Dermatologists, British Journal of Dermatology, 142, 1047±1070 and a partial nail-plate excision was performed almost simultaneously. The lesions reduced progressively until they disappeared. At follow-up 9 months later, the patient remained asymptomatic. The presence of paronychia and excess granulation tissue of the periungual areas has been described during treatment with different drugs such as retinoids. Recently, these same findings were reported in association with antiretroviral agents. The aetiological role of a particular drug on these lesions is difficult to determine, as HIV-positive patients are usually treated with multidrug regimens. The reverse transcriptase inhibitor lamivudine and the protease inhibitor indinavir are the drugs suspected of causing this effect. A patient with severe paronychia due to zidovudine-induced neutropenia has also been described. In our patient, the simultaneous involvement of several nails from distant sites such as the toes and fingers, the lack of similar prior episodes or known risk factors for paronychia, the lack of healing after antibiotic therapy, and the regression once indinavir was withdrawn, suggest that this process was drug-induced and that indinavir was the most likely causative agent for the skin manifestations. Previously reported features include acute paronychia in all patients, and lateral ingrowing nails or formation of granulation tissue in some. The lesions are usually limited to one or both great toes, although fingernails may also be involved. The delay in the appearance of nail complications ranges from 1 to 12 months after the commencement of therapy. Patients differ widely in their degree of immunosuppression. Histological studies are lacking except for those in one patient who showed the histological picture of granulation tissue, similar to our patient. Despite topical or surgical treatment, lesions tend to recur. The development of these lesions seems to be unpredictable, related neither to daily nor to cumulative dose. The course of the lesions after the discontinuation of the suspected drug is not defined in the literature except for six patients with complete or partial regression within 9±12 months. The mechanism by which antiretroviral drugs lead to the development of paronychia and granulation tissue remains unclear. We consider that the description of new cases will delineate the real role of antiretroviral agents on this probably not uncommon, but at present rarely described, side-effect.

Immunohistology of skin and oral biopsies in graft-versus-host disease after bone marrow transplantation and cytokine therapy

BACKGROUND Early diagnosis of graft-versus-host-disease (GVHD) after bone marrow transplantation is often difficult, particularly when the patients are immunosuppressed by chemotherapy or irradiation. OBJECTIVE To investigate the influence of cytokines on skin lesions after bone marrow transplantation. METHODS Biopsy specimens of skin and oral mucosa were obtained from bone marrow transplant patients with GVHD and were subjected to histologic and immunohistochemical examination. RESULTS Administration of granulocyte-macrophage colony-stimulating factor caused atopic dermatitis-like lesions in two patients, who had infiltration of neutrophils, eosinophils, and lymphocytes around the hair follicles of the skin and no signs of GVHD in other organs. Only patients who were treated with cytokines developed acute GVHD. Immunohistochemical examination of skin biopsies from 18 patients with acute GVHD and 11 patients with chronic GVHD after cyclophosphamide administration or irradiation showed that the maculopapular skin lesions characteristic of acute GVHD contained infiltrates of CD4+ and CD8+ lymphocytes. There was also an increase in numbers of epidermal keratinocytes expressing intercellular adhesion molecule-I and HLA-DR antigens. CONCLUSION These findings support the involvement of cytokines in GVHD and suggest that immunostaining of skin biopsies may be useful for the early diagnosis of this condition.