Generation of Antibodies of Distinct Subclasses and Specificity Is Linked to H2s in an Active Mouse Model of Epidermolysis Bullosa Acquisita

Model systems duplicating epidermolysis bullosa acquisita: a methodological review

Epidermolysis bullosa acquisita (EBA) is a chronic mucocutaneous autoimmune skin blistering disease, in which generation of autoantibodies to type VII collagen (COL7) is the key factor for pathogenesis. Much of this current understanding of EBA pathogenesis has been obtained through the development and further application of respective model systems. In vitro model systems of EBA duplicate neutrophil activation by immune complexes of COL7 and anti-COL7 antibodies. Blister induction by anti-COL7 antibodies can be reproduced ex vivo by incubation of cryosections of human skin with anti-COL7 antibodies and neutrophils. Furthermore, EBA can be induced in mice by transfer of human or rabbit anti-COL7 IgG into adult mice, or by immunization of susceptible mouse strains with an immunodominant fragment within the non-collagenous 1 domain of COL7. However, our understanding of EBA pathogenesis is largely limited to mechanisms in autoantibody-induced tissue injury. Furthermore, these model systems of EBA have not been used to a large extent to evaluate the potential of novel treatment options. To foster a broader use of these elaborate model systems to specifically address these open issues, this review focuses on a detailed description of model systems for EBA, which should allow for a broad use of these models. This will hopefully lead to a better understanding of EBA pathogenesis, as well to a benefit in patient care.

Black patients of African descent and HLA-DRB1*15:03 frequency overrepresented in epidermolysis bullosa acquisita

Epidermolysis bullosa acquisita (EBA) is a rare autoimmune bullous disease (AIBD). However, higher EBA incidence and predisposing genetic factor(s) involving an HLA haplotype have been suspected in some populations. This retrospective study assessed the overrepresentation of black patients with EBA, its link with HLA-DRB1*15:03, and their clinical and immunological characteristics. Between 2005 and 2009, 7/13 (54%) EBA and 6/183 (3%) other-AIBD patients seen consecutively in our department were black (P=10(-6)); moreover 7/13 (54%) black patients and 6/183 (3%) white patients had EBA (P=10(-6)). In addition, between 1983 and 2005, 12 black patients had EBA. Finally, among the 19 black EBA patients, most of them had very atypical clinical presentations, 9 were natives of sub-Saharan Africa, 1 from Reunion Island, 7 from the West Indies, and 2 were of mixed ancestry. HLA-DRB1*15:03 allelic frequencies were 50% for African patients, significantly higher than the control population (P<10(-3)), and 21% for the West Indians (nonsignificant). High EBA frequencies have already been reported in American blacks significantly associated with the HLA-DR2. In conclusion, black-skinned patients developing EBA seem to have a genetic predisposition, and EBA should be suspected systematically for every AIBD seen in this population.

Repetitive immunization breaks tolerance to type XVII collagen and leads to bullous pemphigoid in mice

Bullous pemphigoid (BP) is a subepidermal autoimmune blistering disease of the elderly associated with considerable morbidity and mortality. As unspecific immunosuppressants are still the mainstay of BP therapy, several animal models, based on the passive transfer of autoantibodies or immune cells, have been developed to obtain a better understanding of the pathogenesis of BP and evaluate novel therapeutic interventions. We describe in this study an experimental model inducing BP by immunization of immunocompetent mice with a recombinant form of the immunodominant 15th noncollagenous domain of murine BP180 (type XVII collagen). The homologous noncollagenous 16A domain of human BP180 has previously been identified as an immunodominant region in human BP. Immunization of female SJL/J mice with the murine peptide led to clinical disease within 14 wk in 56% of mice. In contrast, none of the other strains developed blisters despite the presence of autoantibodies. The clinical disease manifested for at least 8 wk without further manipulation. This novel immunization-induced model reflects key immunopathological characteristics of human BP, including binding of complement-fixing autoantibodies along the dermal-epidermal junction, elevated total IgE serum levels, and infiltration of skin lesions with eosinophilic granulocytes. The use of immunocompetent mice and the induction of sustained clinical disease not requiring additional interventions make this immunization-induced mouse model most suitable to further explore the pathogenesis of BP and novel therapeutic interventions for this and other autoantibody-mediated diseases.

Heat-shock protein 90 inhibition in autoimmunity to type VII collagen: evidence that nonmalignant plasma cells are not therapeutic targets

Blocking heat-shock protein 90 (Hsp90) induces death of malignant plasma cells by activation of the unfolded protein response, a signaling pathway activated by accumulation of misfolded proteins within the endoplasmic reticulum. We hypothesized that nontransformed plasma cells are also hypersensitive to Hsp90 inhibition because of their high amount of protein biosynthesis. To investigate this hypothesis, 2 different Hsp90 inhibitors, the geldanamycin derivative 17-DMAG and the nontoxic peptide derivative TCBL-145, were applied to mice with experimental epidermolysis bullosa acquisita, an autoimmune bullous disease characterized by autoantibodies against type VII collagen of the dermal-epidermal junction. Both inhibitors ameliorated clinical disease of type VII collagen-immunized mice, suppressed auto-antibody production, and reduced dermal neutrophilic infiltrate. Interestingly, total plasma cell numbers, type VII collagen-specific plasma cells, and germinal center B cells were unaffected by anti-Hsp90 treatment in vivo. However, T-cell proliferation was potently inhibited, as evidenced by the reduced response of isolated lymph node cells from immunized mice to in vitro restimulation with anti-CD3/CD28 antibody or autoantigen in the presence of Hsp90 inhibitors. Our results suggest that Hsp90 blockade has no impact on normal or autoreactive plasma cells in vivo and indentify T cells as targets of anti-Hsp90 treatment in autoimmunity to type VII collagen.