Predominant IgG4 subclass in autoantibodies of pemphigus vulgaris and foliaceus.

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) are autoimmune skin diseases caused by autoantibodies against desmoglein (Dsg) 3 and Dsg1. We have previously developed ELISAs using recombinant Dsg3 and Dsg1 expressed by baculovirus as a diagnostic tool for pemphigus. In this study, we determined the frequency of coexistence of IgA class as well as distribution of IgG subclass. Two out of 49 PV and PF sera tested had anti-Dsg1 IgA in addition to anti-Dsg1 IgG. Interestingly, one of them showed prominent pustular formation. Among IgG subclass, IgG4 was predominant and found in all of the 30 PV and 19 PF sera tested, followed by IgG1, detected in 25 out of 30 PV and 12 out of 19 PF sera. Even though IgG2 and IgG3 were detected in 13 and one PV and 6 and 4 PF sera, respectively, the ELISA titers had barely exceeded the cutoff value in most of the cases. There was no IgG subclass shift during the course of the disease in seven cases examined. These findings indicate that IgG4 subclass is the predominant autoantibodies in both PV and PF, while IgG1 is also frequently found.