Discrepancy between the localization of in vivo bound immunoglobulins in the skin and in vitro binding sites of circulating anti-BMZ antibodies in bullous pemphigoid: immunoelectron microscopic studies.

The immunoelectron microscopic reaction products showing in vivo bound immunoglobulins or complement in the basement membrane zone (BMZ) of the lesional skin of 12 patients with bullous pemphigoid (BP) were homogeneously distributed in the lamina lucida in 3 cases, just beneath the basilar surface of the basal cells in 5 cases, and were associated with the basal lamina in 4 cases. No reaction products could be found beneath the melanocytes in any of the first 2 groups; however, positive reaction products were found on the basal lamina beneath some melanocytes, and were associated with the detached basal lamina in the dermis in the latter 4 cases. In vitro binding sites of circulating anti-BMZ antibodies in the sera from 7 patients with BP indicated that the antibodies reacted with the basilar surface of the hemidesmosomes, with a weak reaction on the basal lamina in 5 cases and with no reaction in 2 cases. No positive findings were obtained beneath the melanocytes or on the basal lamina under the melanocytes. The discrepancy between the antigenic sites and the localization of immune deposits in BP is assumed to be due to the renewal of the hemidesmosomes and constant clearance of immune deposits in vivo. The in vivo bound immunoglobulins and complement seen in the BP skin are the result of their accumulation in the lamina lucida or in association with the basal lamina.