Determination of IgG subclasses in patients with pemphigus with active disease and in remission.

IgG subclasses were determined in perilesional skin of 13 patients with pemphigus with active disease and of 14 patients in a state of clinical remission. Using indirect immunofluorescence technique, frozen sections were incubated with mouse monoclonal antihuman IgG1, IgG2, IgG3, and IgG4 followed by a second incubation with fluorescein isothiocyanate-conjugated goat antimouse IgG. The results showed that among patients with active disease, IgG1 was found in all of them and IgG4 in 85%, while IgG2 and IgG3 were found in 54% and 77%, respectively. For patients in remission the most common subclass was IgG4 in 79% of patients, and in a decreased order IgG1, 50%; IgG3, 29%; and IgG2, 14%. It appears that IgG1 and IgG4 are predominant among patients with active lesions. IgG1 seems to be the most sensitive indicator for activity of the disease. IgG4, normally found in the lowest concentration in human serum, is the most common subclass in patients who are in remission. IgG3 and C3 may have a predictive value for remission.