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In this study, an in vitro model of immune complex-mediated basement membrane zone separation caused by periphigoid antibodies, serum complement, and peripheral blood leukocytes is described. When cryostat sections of fresh-frozen normal human skin were treated with either of 4 bullous pemiphigoid sera containing complement-activating anti-basement membrane zone antibodies and subsequently incubated at 37 degrees C with normal human peripheral blood leukocytes and fresh human serum, leukocytes attached to 96% of the basement membrane zone in 100% of sections. Sixty-seven percent of the sections developed focal areas of basement membrane zone separation resembling dermal-epidermal separation described in early pemphigoid lesions. In control sections in which either leukocytes, pemphigoid antibody or fresh human serum were omitted, significantly less leukocyte attachment and basement membrane zone separation occurred. Evidence that leukocytes caused separation was supported by an absolute requirement for viable leukocytes during incubation, a high correlation between leukocyte attachment and separation and experiments showing that leukocytes attached to the basement membrane zone were activated. This study provides the first in vitro evidence directly supporting a functional role for immune-complex mediated inflammation in the pathogenesis of basement membrane zone separation and blisters in bullous pemphigoid.

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To study the mechanisms responsible for leukocytoclastic vasculitis, we evaluated the kinetics of immunologic and cellular changes in induced vasculitis lesions. In four of five consecutive patients with active vasculitis, lesions were induced by increasing vascular permeability via injecting histamine into the skin. Biopsies were obtained for light and electron microscopy and immunofluorescence at 1, 4, 8, and 24 hr after injection. The results show that immunoglobulin, C3, and electron-dense material are deposited in vessel walls early and are followed by cellular infiltration. The characteristics of the cellular infiltrates were quite diverse at different times after histamine provocation and no distinctive patterns were seen. Nevertheless, the kinetics of the appearance of immunoreactants and cells implies that immunoglobulin and probably circulating immune complexes are present prior to the development of inflammation and supports the contention that deposition of immune complexes within vessel walls is responsible for leukocytoclastic vasculitis.

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