The complement fixing ability of anti-basement membrane zone IgG subclass of herpes gestationis and bullous pemphigoid.

The antibody activities and complement fixing ability of the IgG subclass antibodies of herpes gestationis (HG) and bullous pemphigoid (BP) antibodies were investigated. IgG was prepared by DEAE Affi-Gel Blue column. IgG3 and IgG 1.2.4 fractions were isolated through Protein-A Sepharose CL-4B column. In HG, neither IgG nor C3 deposits were detected at the basement membrane zone (BMZ) in the skins incubated with IgG3 fractions, although C3 deposits were detected without IgG deposits in the skins incubated with IgG 1.2.4 fractions. In BP, IgG and C3 deposits were detected in the skins incubated with IgG3 fractions, while neither IgG nor C3 deposits were detected in the skins incubated with IgG3 fractions. These findings suggest that IgG3 might not be able to fix complement at BMZ in BP and HG, although there are some reports that complement activating ability of IgG3 is the strongest among IgG subclasses.