The distribution of IgG subclasses in pemphigoid gestationis: PG factor is an IgG1 autoantibody.

Using monoclonal antibodies in immunofluorescence techniques, the subclass distribution of anti-basement membrane zone IgG antibodies was studied in the skin, placenta, and serum of patients with pemphigoid (herpes) gestationis. IgG1 was found to be the major IgG subclass in both serum and tissue, being detected in the sera of all pemphigoid gestationis patients studied. In pemphigoid and pemphigus, however, the distribution of IgG subclasses was heterogeneous, with IgG4 being the dominant autoantibody. Pemphigoid (herpes) gestationis factor, the circulating anti-basement membrane zone autoantibody thought to be pathogenic in pemphigoid gestationis, is therefore, an IgG1 antibody, with inferred complement binding capacity. Tissue damage in pemphigoid gestationis is apparently mediated by complement fixation which is detected via the classical complement cascade.