Subclass distribution of IgG autoantibodies in bullous pemphigoid.

The distribution of IgG subclasses in the antibasement membrane zone autoantibody of pemphigoid in skin and serum was analyzed by use of monoclonal antibodies to human IgG subclasses. The predominant subclass was IgG4 which was present in 23 of 24 skin biopsies, IgG1 was next and IgG3 was found only occasionally. In 3 of 24 biopsies IgG4 was the only IgG subclass detected, C3 was absent in 2 of these, the third contained IgM and C3. Serum autoantibodies were similarly analyzed by indirect immunofluorescence (IIF) when again IgG4 autoantibody was the dominant subclass. No IgE autoantibody was detected by IIF.