Correlation of subclasses of IgG with disease activity in pemphigus vulgaris.

Pemphigus vulgaris is an autoimmune blistering disease that is characterized by the presence of an antibody against an epidermal cell protein. In our previous studies, we have demonstrated that the presence of the antibody in the patients and in the healthy relatives of the patients strongly correlates with MHC haplotypes. The purpose of this study was to determine the subclasses of IgG present in the sera of patients with active disease, those in remission, healthy and unaffected relatives and normal controls. The presence of the autoantibody to the pemphigus antigen was assayed by a modified, sensitive immunoblot technique. The assay was considered positive if a 130-kD band was seen when normal human epidermis was used as a substrate. In patients with active disease, the sera contained antibodies of the IgG1 and IgG4 subclasses. The sera of patients in remission, those of healthy unaffected relatives and normal controls contained only the IgG1 subclass. The normal controls consist of MHC-matched and nonmatched individuals. This study indicates that patients with disease activity have an antibody which is of the IgG1 and IgG4 subclasses, which we consider to be a pathogenic antibody. The sera of healthy relatives and normal controls that contain an antibody which binds to the pemphigus antigen is of the IgG1 subclass only and is considered to be a nonpathogenic or natural autoantibody. These observations provide the basis to study the immunoregulatory mechanisms and the production of normal and pathogenic antibodies.