Yohei Natsuaki

Perivascular leukocyte clusters are essential for efficient activation of effector T cells in the skin

It remains largely unclear how antigen-presenting cells (APCs) encounter effector or memory T cells efficiently in the periphery. Here we used a mouse contact hypersensitivity (CHS) model to show that upon epicutaneous antigen challenge, dendritic cells (DCs) formed clusters with effector T cells in dermal perivascular areas to promote in situ proliferation and activation of skin T cells in a manner dependent on antigen and the integrin LFA-1. We found that DCs accumulated in perivascular areas and that DC clustering was abrogated by depletion of macrophages. Treatment with interleukin 1α (IL-1α) induced production of the chemokine CXCL2 by dermal macrophages, and DC clustering was suppressed by blockade of either the receptor for IL-1 (IL-1R) or the receptor for CXCL2 (CXCR2). Our findings suggest that the dermal leukocyte cluster is an essential structure for elicitating acquired cutaneous immunity.

Intravital analysis of vascular permeability in mice using two-photon microscopy

Blood vessel endothelium forms a semi-permeable barrier and its permeability controls the traffics of plasma contents. Here we report an intravital evaluation system for vascular permeability in mice using two-photon microscopy. We used various sizes of fluorescein-conjugated dextran as a tracer and its efflux was quantified by measuring the changes of fluorescent intensity both on the blood vessel area and the interstitial space. Using this system, we demonstrated that skin blood vessels limited the passage of dextran larger than 70 kDa under homeostatic conditions. We evaluated the kinetics of vascular permeability in histamine- or IgE-induced type I allergic models and a hapten-induced type IV allergic model. In such inflammatory conditions, the hyperpermeability was selectively induced in the postcapillary venules and dextran as large as 2000-kDa leaked from the bloods. Taken together, our study provides a convenient method to characterize the skin blood vessels as a traffic barrier in physiological conditions.

IL-17A as an Inducer for Th2 Immune Responses in Murine Atopic Dermatitis Models

Atopic dermatitis (AD) is generally regarded as a type 2 helper T (Th2)-mediated inflammatory skin disease. Although the number of IL-17A-producing cells is increased in the peripheral blood and in acute skin lesion of AD patients, the role of IL-17A in the pathogenesis of AD remains unclear. To clarify this issue, we used murine AD models in an IL-17A-deficient condition. In a repeated hapten application-induced AD model, skin inflammation, IL-4 production in the draining lymph nodes (LNs), and hapten-specific IgG1 and IgE induction were suppressed in IL-17A-deficient mice. Vγ4(+) γδ T cells in the skin-draining LNs and Vγ5(-) dermal γδ T cells in the skin were the major sources of IL-17A. Consistently, in flaky-tail (Flg(ft/ft) ma/ma) mice, spontaneous development of AD-like dermatitis and IgE induction were attenuated by IL-17A deficiency. Moreover, Th2 differentiation from naive T cells was promoted in vitro by the addition of IL-17A. Taken together, our results suggest that IL-17A mediates Th2-type immune responses and that IL-17A signal may be a therapeutic target of AD.

From anti-p200 pemphigoid to anti-laminin γ1 pemphigoid

Anti‐laminin γ1 pemphigoid is an autoimmune subepidermal bullous disease first described in 1996, and has been distinct from previously known subepidermal blistering diseases, such as bullous pemphigoid and epidermolysis bullosa acquisita. Circulating autoantibodies of the patients do not react to any known autoantigen of the skin, but react to a 200‐kDa molecule (p200) from dermal extracts. The identity of p200 was unmasked as laminin γ1, an extracellular matrix glycoprotein composing several forms of laminin heterotrimers. We renamed this disease from the previously used anti‐p200 pemphigoid to anti‐laminin γ1 pemphigoid, a new entity of an autoimmune bullous disease. In this decade, we have experienced over 70 cases of this disease. Although the number of the cases of anti‐laminin γ1 pemphigoid is half as many as the number of definitely diagnosed cases of epidermolysis bullosa acquisita in the same duration, a considerable number of the cases could be clinically misdiagnosed as epidermolysis bullosa acquisita. Unveiling the pathogenicity and development of a useful diagnostic method is necessary for appropriate management of this new disease.

An ITAM-Syk-CARD9 signalling axis triggers contact hypersensitivity by stimulating IL-1 production in dendritic cells

A variety of reactive organic compounds, called haptens, can cause allergic contact dermatitis. However, the innate immune mechanisms by which haptens stimulate dendritic cells (DCs) to sensitize T cells remain unclear. Here we show that the coupling of ITAM-Syk-CARD9 signalling to interleukin-1 (IL-1) secretion in DCs is crucial for allergic sensitization to haptens. Both MyD88 and Caspase recruitment domain-containing protein 9 (CARD9) signalling are required for contact hypersensitivity (CHS). Naïve T cells require signals received through IL-1R1-MyD88 for effector differentiation, whereas DCs require CARD9 and spleen tyrosine kinase (Syk) signalling for hapten-induced IL-1α/β secretion and their ability to prime T cells. DC-specific deletion of CARD9, DAP12, Syk or NLRP3, but not MyD88, is sufficient to abolish CHS. All tested haptens, but not irritants, can induce Syk activation, leading to both the CARD9/BCL10-dependent pro-IL-1 synthesis (signal1) and reactive oxygen species-mediated NLRP3 inflammasome activation (signal2), required for IL-1 secretion. These data unveil an innate immune mechanism crucial for allergic contact sensitization to chemical compounds.

Five Japanese cases of antidesmoglein 1 antibody‐positive and antidesmoglein 3 antibody‐negative pemphigus with oral lesions

Background  Oral mucosal lesions develop in pemphigus vulgaris, but not in pemphigus foliaceus. This clinical phenomenon is explained by the ‘desmoglein (Dsg) compensation theory’. Dsg3 and Dsg1 are major autoantigens for pemphigus vulgaris and pemphigus foliaceus, respectively. Dsg3 is overexpressed and Dsg1 is weakly expressed on the oral mucosa. Thus, on the oral mucosa, suppression of Dsg3 function by anti‐Dsg3 autoantibodies is not compensated by weakly expressed Dsg1 in pemphigus vulgaris, while suppression of Dsg1 function by anti‐Dsg1 autoantibodies is perfectly compensated by richly expressed Dsg3 in pemphigus foliaceus.

Anti-Alpha-2-Macroglobulin-Like-1 Autoantibodies Are Detected Frequently and May Be Pathogenic in Paraneoplastic Pemphigus

Paraneoplastic pemphigus (PNP) shows autoantibodies mainly to plakin and desmosomal cadherin family proteins. We have recently identified alpha-2-macroglobulin-like-1 (A2ML1), a broad range protease inhibitor, as a unique PNP antigen. In this study, we tested a large number of PNP sera by various methods. Forty (69.0%) of 58 PNP sera recognized A2ML1 recombinant protein expressed in COS7 cells by immunofluorescence (IF) and/or immunoprecipitation (IP)/immunoblotting (IB). IP/IB showed higher sensitivity than IF. In addition, 22 (37.9%) PNP sera reacted with A2ML1 by IB of cultured normal human keratinocytes (NHKs) under non-reducing conditions. Statistical analyses using various clinical and immunological data showed that the presence of anti-A2ML1 autoantibodies was associated with early disease onset and absence of ocular lesions. Next, to investigate the pathogenic role of anti-A2ML1 antibody, we performed additional functional studies. Addition of anti-A2ML1 polyclonal antibody to culture media decreased NHK cell adhesion examined by dissociation assay, and increased plasmin activity detected by casein zymography, suggesting that anti-A2ML1 antibody may decrease NHK cell adhesion through plasmin activation by inhibition of A2ML1. This study demonstrates that autoantibodies to A2ML1 are frequently and specifically detected and may have a pathogenic role in PNP.

Interaction of plectin and intermediate filaments.

BACKGROUND Plectin, a member of the plakin family proteins, is a high molecular weight protein that is ubiquitously expressed. It acts as a cytolinker for the three major components of the cyotoskeleton, namely actin microfilaments, microtubules and intermediate filaments. OBJECTIVE The aim of our experiments was to identify new binding sites for intermediate filaments on plectin and to specify these sites. METHODS We introduced truncated forms of plectin into several cell lines and observe interaction between plectin and intermediate filaments. RESULTS We found that a linker region in the COOH-terminal end of plectin was required for the association of the protein with intermediate filaments. In addition, we also demonstrated that a serine residue at position 4645 of plectin may have a role on binding of plectin to intermediate filaments. CONCLUSION A linker region in the COOH-terminal end and serine residue at position 4645 may be important for the binding of plectin to intermediate filaments.

Distinct protein expression and activity of transglutaminases found in different epidermal tumors

We investigated protein expression and in situ activity of transglutaminases (TGs) in normal skin and various epidermal neoplasms. In normal skin, TG1 protein expression and TG activity were found at keratinocyte cell membranes in upper epidermis and granular layer, respectively. In seborrhoeic keratosis, TG1 protein was expressed evenly throughout tumors, while TG activity increased in gradient fashion from lower tumor area to cornified layer. In squamous cell carcinoma, TG1 protein was expressed at inner side of cell membranes, whereas TG activity was found in cytoplasm predominantly at horn pearls. In basal cell carcinoma, weak TG activity was found in cytoplasm of all tumor cells without the presence of TG1 protein. Immunoblotting and in situ activity assays using specific substrate peptides confirmed that TG2, but not TG1, contributed to the TG activity. These results suggested that different expression and activation of TGs may contribute to characteristics of the skin tumors.

Decline of disease activity and autoantibodies to desmoglein 3 and envoplakin by oral prednisolone in paraneoplastic pemphigus with benign thymoma.

ejd.2012.1742 Auteur(s) : Norito Ishii, Takahiro Hamada, Hiroshi Koga, Ryosuke Sogame, Bungo Ohyama, Shunpei Fukuda, Yohei Natsuaki, Teruki Dainichi, Tadashi Karashima, Takekuni Nakama, Daisuke Tsuruta, Takashi Hashimoto hashimot@med.kurume-u.ac.jp Department of Dermatology, Kurume University School of Medicine, Kurume University Institute of Cutaneous Cell Biology, Fukuoka 830-0011, Japan A 79-year-old Japanese female presented with a 2-month history of painful oral mucosal erosions and skin lesions [...]