Identification of IgA subclasses in skin of dermatitis herpetiformis patients.

There is a controversy as to the origin and to the subclass of IgA in dermatitis herpetiformis (DH) skin. The present study was undertaken to reexamine the subclasses of IgA and the presence of J-chain in biopsies of DH patients. Skin biopsies from 12 DH patients were examined for IgA, its subclasses and for J-chain by a modified direct immunofluorescence (IF) method. All DH skin biopsies were positive for IgA. Ten of the twelve biopsies were positive for IgA1. IgA2 was detected in only 3 cases, notably in those which gave the strongest IgA reactions. In general, the fluorescent staining intensity for IgA2 was weaker than IgA1 and IgA1 was less than the total IgA. This may be due to differences in the concentrations of the immunoglobulin subclasses in the skin and may also be due to the restricted specificity of antisera used in the study. Direct IF studies of the presence of J-chain yielded negative findings in all DH cases examined including those which were positive for IgA2. The higher frequency of IgA1 over that of IgA2 and the absence of J-chain indicate that the IgA immune deposits in the DH skin may not necessarily be of mucosal origin.