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.