IgA in dermatitis-herpetiformis skin is dimeric.

Skin-biopsy specimens from six patients with dermatitis herpetiformis (DH) were examined by means of indirect immunofluorescence with specific rabbit antisera for the presence of in-vivo J chain and secretory component in IgA deposits. The ability of IgA to bind purified secretory component was studied by means of indirect immunofluorescence with antisera to secretory component. Positive J-chain staining associated with IgA deposits was seen in cryostat sections of all seven DH skin-biopsy specimens. In-vivo secretory component was not detected, but on treatment of sections with a solution of purified secretory component, binding of the latter in the region of the IgA deposits was demonstrated in six of the seven DH skin-biopsy specimens. With double fluorochrome staining binding of secretory component was shown to be essentially coextensive with the IgA deposits. These findings suggest that the IgA deposited in DH skin originates from plasma cells in the small intestine.