Herpes gestationis: studies on the binding characteristics, activity and pathogenetic significance of the complement-fixing factor.

The sera of seven out of eight patients with Herpes gestationis contained a factor which fixed C3 but not detectable amounts of immunoglobulin (Ig) on the basement membrane zone (BMZ) of normal human skin. Using C2-deficient human serum and C4-deficient guinea-pig serum, fixation was shown to be dependent upon activation of the classical pathway, and chromatography and immunoabsorption studies indicated the H. gestationis factor to be an IgG immunoglobulin. In all seven sera the H. gestationis factor bound to, and could be eluted from, the eluate of staphylococcal protein A. Although the H. gestationis factor failed to block staining of human sera by a FITC-conjugated antibody prepared from bullous pemphigoid (BP) serum, complement fixation by five out of seven sera of patients with H. gestationis was blocked using F(ab')2 of IgG prepared from pooled BP serum. In a single patient rapid resolution of lesions followed plasma exchange on two separate occasions, indicating the pathogenetic importance of humoral factors in this disease.