Reine Moriuchi

A Novel Active Mouse Model for Bullous Pemphigoid Targeting Humanized Pathogenic Antigen

Bullous pemphigoid (BP), the most common autoimmune blistering disease, is caused by autoantibodies against type XVII collagen (COL17). To establish an active stable BP animal model that demonstrates the persistent inflammatory skin lesions initiated by the anti-human COL17 Abs, we used COL17-humanized (COL17m−/−,h+) mice that we recently produced. First, we generated immunodeficient Rag-2−/−/COL17–humanized mice by crossing Rag-2−/− mice with COL17-humanized mice. Then, splenocytes from wild-type mice that had been immunized by grafting of human COL17-transgenic mouse skin were transferred into Rag-2−/−/COL17–humanized mice. The recipient mice continuously produced anti-human COL17 IgG Abs in vivo and developed blisters and erosions corresponding to clinical, histological, and immunopathological features of BP, although eosinophil infiltration, one of the characteristic histological findings observed in BP patients, was not detected in the recipients. Although the depletion of CD8+ T cells from the immunized splenocytes was found to produce no effects in the recipients, the depletion of CD4+ T cells as well as CD45R+ B cells was found to inhibit the production of anti-human COL17 IgG Abs in the recipients, resulting in no apparent clinical phenotype. Furthermore, we demonstrated that cyclosporin A significantly suppressed the production of anti-human COL17 IgG Abs and prevented the development of the BP phenotype in the treated recipients. Although this model in an immunodeficient mouse does not exactly reproduce the induction mechanism of BP in human patients, this unique experimental system targeting humanized pathogenic Ag allows us to investigate ongoing autoimmune responses to human molecules in experimental animal models.

Human IgG1 Monoclonal Antibody against Human Collagen 17 Noncollagenous 16A Domain Induces Blisters via Complement Activation in Experimental Bullous Pemphigoid Model

Bullous pemphigoid (BP) is an autoimmune blistering disease caused by IgG autoantibodies targeting the noncollagenous 16A (NC16A) domain of human collagen 17 (hCOL17), which triggers blister formation via complement activation. Previous in vitro analysis demonstrated that IgG1 autoantibodies showed much stronger pathogenic activity than IgG4 autoantibodies; however, the exact pathogenic role of IgG1 autoantibodies has not been fully demonstrated in vivo. We constructed a recombinant IgG1 mAb against hCOL17 NC16A from BP patients. In COL17-humanized mice, this mAb effectively reproduced a BP phenotype that included subepidermal blisters, deposition of IgG1, C1q and C3, neutrophil infiltration, and mast cell degranulation. Subsequently, alanine substitutions at various C1q binding sites were separately introduced to the Fc region of the IgG1 mAb. Among these mutated mAbs, the one that was mutated at the P331 residue completely failed to activate the complement in vitro and drastically lost pathogenic activity in COL17-humanized mice. These findings indicate that P331 is a key residue required for complement activation and that IgG1-dependent complement activation is essential for blister formation in BP. This study is, to our knowledge, the first direct evidence that IgG1 Abs to hCOL17 NC16A can induce blister formation in vivo, and it raises the possibility that IgG1 mAbs with Fc modification may be used to block pathogenic epitopes in autoimmune diseases.

Circulating IgA and IgE autoantibodies in antilaminin-332 mucous membrane pemphigoid

Background  Antilaminin‐332 mucous membrane pemphigoid (MMP) is a chronic autoimmune bullous disease that is often associated with internal malignancy. IgG autoantibodies against laminin‐332 in patients with MMP are well documented; however, IgA and IgE autoantibodies against laminin‐332 have not yet been described.

Noncollagenous 16A domain of type XVII collagen-reactive CD4+ T cells play a pivotal role in the development of active disease in experimental bullous pemphigoid model

Bullous pemphigoid (BP), the most common autoimmune blistering disease, is caused by autoantibodies against type XVII collagen (COL17). We recently demonstrated that CD4+ T cells were crucial for the production of anti-COL17 IgG and for the development of the BP phenotype by using a novel active BP mouse model by adoptively transferring immunized splenocytes into immunodeficient COL17-humanized mice. Noncollagenous 16A (NC16A) domain of COL17 is considered to contain the main pathogenic epitopes of BP, however, the pathogenicity of COL17 NC16A-reactive CD4+ T cells has never been elucidated. To address this issue, we modulated the immune responses against COL17 in active BP model by using anti-CD40 ligand (CD40L) monoclonal antibody MR1, an inhibitor of the CD40-CD40L interaction, in various ways. First, we show the essential role of CD4+ T cells in the model by showing that CD4+ T cells isolated from wild-type mice immunized with human COL17 enabled naïve B cells to produce anti-COL17 NC16A IgG in vivo. Second, we show that the activation of anti-COL17 NC16A IgG-producing B cells via CD40-CD40L interaction was completed within 5 days after the adoptive transfer of immunized splenocytes. Notably, a single administration of MR1 at day 0 was enough to inhibit the production of anti-COL17 NC16A IgG and to diminish skin lesions despite the presence of restored anti-COL17 IgG at the later stage. In contrast, the delayed administration of MR1 failed to inhibit the production of anti-COL17 NC16A IgG and the development of the BP phenotype. These results strongly suggest that COL17 NC16A-reactive CD4+ T cells play a pivotal role in the production of pathogenic autoantibodies and in the development of active disease in experimental BP model.

Papuloerythroderma of Ofuji associated with early gastric cancer

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Neonatal vesiculopustular eruption of the face: a sign of trisomy 21-associated transient myeloproliferative disorder

SIR, Neonatal vesiculopustular eruptions suggest a number of differential diagnoses including both infectious and noninfectious aetiologies. We describe a phenotypically normal neonate with a vesiculopustular eruption arising from birth as the result of a transient myeloproliferative disorder (TMD) associated with mosaic trisomy 21. In November 2005, a Japanese girl was born at 39 weeks’ gestation, the second child of a healthy 25-year-old woman. Shortly after birth, bizarre vesiculopustular skin lesions were observed on her face, and rapidly increased in number with a tendency to appear at sites where pressure or dressings had been applied. There was no maternal history of genital herpes simplex virus infection, and application of topical aciclovir by the attending paediatrician failed to improve the skin lesions. She was referred to the dermatology clinic on day of life (DOL) 14. Physical examination revealed 3to 6-mm, reddish, small vesicular papules with yellowish crusts scattered on her face, especially on the cheeks (Fig. 1). Bacterial culture from the eruption resulted in a marginal growth of Staphylococcus aureus, Enterococcus faecalis and methicillin-resistant S. aureus. Skin biopsy of a papule on her left cheek revealed prominent infiltration of mononuclear cells with slightly atypical nuclei within the epidermis and upper dermis. There were no viral inclusions, ballooning or reticular degeneration in the epidermis (Fig. 2a). The myeloid lineage of these mononuclear cells was confirmed using myeloperoxidase staining (Fig. 2b). The baby had experienced shortness of breath on DOL 4. At the time of this episode, the white blood cell (WBC) count was 99Æ7 · 10 L, with blast cells. Acute myelogenous leukaemia (AML) was suspected; however, bone marrow aspiration demonstrated no blast cells. Thus she was diagnosed as having TMD. As TMD is known to occur mainly in infants with Down syndrome, peripheral blood fluorescence in situ hybridization (FISH) was performed. Although she was phenotypically normal, FISH analysis revealed mosaicism for trisomy 21. The vesiculopustular eruption was resistant to topical antibiotics (gentamicin or fusidic acid) and remained unchanged until DOL 17. Later, the eruption showed a tendency to improve as the WBC count decreased smoothly, and spontaneously cleared without any additional intervention at 2 months of age. Further follow-up of her blood counts at intervals of 3 months revealed no sign of haematological malignancy, and she remains healthy at 1 year of age. (a)

Low-dose etretinate shows promise in management of punctate palmoplantar keratoderma type 1: Case report and review of the published work

Punctate palmoplantar keratoderma type 1 (PPKP1) is a rare autosomal dominant disorder of keratinization, clinically characterized by punctate keratotic papules affecting the palmoplantar skin. Loss‐of‐function mutations in AAGAB have recently been reported as a cause of PPKP1. Despite the discovery of the genetic cause of PPKP1, pathogenesis‐based therapies are still unavailable. Moreover, little is known about the effectiveness of treatments for PPKP1. In this study, we analyzed a Japanese woman with PPKP1 and identified a novel frame‐shift mutation c.195_198del4 (p.Lys66Phefs*43) in AAGAB. Moreover, low‐dose etretinate was effective in improving the PPKP1 lesions in our patient. Our published work review identified only eight cases of PPKP1 with successful response to topical or systemic treatments. Notably, six of the cases were successfully treated with systemic retinoids. Thus, this study clearly provides further evidence that PPKP1 is caused by AAGAB mutations and that systemic retinoids are the most promising current treatment for PPKP1.

Childhood subepidermal blistering disease with autoantibodies to type VII collagen and laminin-332

MADAM, Autoimmune subepidermal blistering diseases include bullous pemphigoid, pemphigoid gestationis, linear IgA bullous dermatosis, mucous membrane pemphigoid (MMP), antip200 pemphigoid, epidermolysis bullosa acquisita (EBA) and bullous systemic lupus erythematosus. Patients with EBA have IgG autoantibodies to type VII collagen while some patients with MMP have autoantibodies to laminin-332. We describe a juvenile case of subepidermal blistering disease with autoantibodies to both type VII collagen and laminin-332. The present case is unique because of its childhood onset and successful remission following only topical steroid therapy. A 12-year-old Japanese girl presented with pruritic eruptions on her scalp. A few weeks later, widespread pruritic vesicles gradually developed over her whole body. The vesicles were seen both on erythematous and normal skin (Fig. 1a, b). Blisters and erosions also appeared in her oral mucosa, but there was no involvement of genital or ocular mucous membranes (Fig. 1c). Neither nail changes nor alopecia were observed. She had no family history of any blistering disorders or autoimmune disease. There was no preceding illness or history of medication ⁄vaccination that might have triggered her disease. General laboratory examinations revealed no apparent abnormalities except for an increased serum IgE level (668Æ8 IU mL; normal < 100 for age 7–14 years). A skin biopsy was taken from the edge of one blister on her right forearm. Light microscopy showed a subepidermal blister with an inflammatory cell infiltrate consisting of mainly neutrophils in the upper dermis (Fig. 2a). Direct immunofluorescence of the patient’s lesional skin showed in vivo linear deposits of IgG and C3 at the epidermal basement membrane zone (Fig. 2b). On the blistered area, deposition of IgG and C3 was demonstrated on the dermal side of the separated skin (arrows, Fig. 2b). Indirect immunofluorescence with the patient’s serum on 1 mol L NaCl-split normal human skin showed IgG antibodies bound to the dermal side of the blister (Fig. 2c). Immunoblot analysis revealed that the patient’s serum reacted with a 290-kDa protein in dermal extracts, and further with purified laminin-332 a3 protein (145, 165 kDa) (Fig. 2d, e). Laminin-332 was obtained from human keratinocytes and was purified using an antilaminin-332 affinity column as BJD British Journal of Dermatology

A novel ATP2A2 missense mutation p.Asp254Gly in Darier disease restricted to the extremities

diagnosis of GS type 2. Sequencing of the RAB27A gene showed a new homozygous mutation, 514 del CAAGC, in the sixth exon of the RAB27A gene. Both parents were heterozygous for the same mutation. Interestingly, this new frame shift mutation is very close to the mutation 510delAAGCC, which was described before in identical Turkish twins. His pneumonic infiltration was treated with antibiotics. Hemophagocytic syndrome responded well to treatment with dexamethasone, etoposide, cyclosporine A, and blood transfusion. Bone-marrow transplantation has been planned. The patient is now 20 months old and on regular follow-up.

Large subcutaneous abscesses caused by Mycobacterium fortuitum infection.

Sir, The non-tuberculous mycobacteria (NTM) are a heterogeneous group of acid-fast bacilli which differ from Mycobacterium tuberculosis. With the advent of the AIDS epidemic and the introduction of immunosuppressive therapies, the incidence of NTM-associated diseases has risen (1). In healthy individuals, cutaneous infection with NTM usually results in small abscess with sinus formation, whilst in immunocompromised hosts the abscess tend to be multiple and widespread (2, 3). We describe here an unusual case of a young healthy woman who developed multiple large subcutaneous abscesses caused by M. fortuitum.