Fig. 3.

IgG4 autoantibodies, in contrast to IgG1, do not fix complement to the dermal–epidermal junction in bullous pemphigoid. Cryosections of normal human skin were incubated with serum and immunoaffinity purified IgG1 and IgG4 antibody preparations from a bullous pemphigoid patient and, subsequently, treated with normal human serum as a source of complement. Both a serum and b purified IgG1 autoantibodies fixed complement C3 at the dermal–epidermal junction in a linear fashion. c In contrast, incubation of cryosections with IgG4 specific for the dermal–epidermal junction does not result in C3 deposition (all magnifications, ×200)