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The complement system in bullous pemphigoid: VII. Fixation of the regulatory protein beta 1H globulin by pemphigoid antibody.

Using in vitro complement immunofluorescent staining methods, serum samples from 5 active cases of bullous pemphigoid, with pemphigoid antibody titers of 320 or greater, were tested for their ability to fix the regulatory protein beta 1H globulin in addition to C4 and C3. All 5 samples yielded positive C3, C4 and beta 1H staining reactions in a linear fashion along the basement membrane zone. Heat inactivation or treatment of the complement source (fresh normal human serum) with EDTA, Mg2-EGTA abolished all 3 staining reactions. Substitution of C2-deficient serum as the source of complement inhibited both C3 and beta 1H staining but had no effect on C4 staining. Use of serum devoid of beta 1H (R beta 1H) minimally enhanced C3 staining while no beta 1H staining was observed. The addition of beta 1H to R beta 1H restored positive beta 1H staining. Skin biopsies of perilesional skin from 6 patients with bullous pemphigoid demonstrated heavy in vivo deposition of beta 1H in addition to C3. These studies suggest that pemphigoid antibodies will fix the regulatory protein beta 1H in addition to other complement components, a phenomenon which requires activation of the classical complement pathway and generation of the C3b amplification convertase.