Immunopathology of the placenta in pemphigoid gestationis and linear IgA disease

We have investigated the immunopathology of the placenta in bullous diseases by studying the deposition of immune complexes and expression of MHC class II subregion products by immunohistological methods. Placentae from seven patients with pemphigoid gestationis (PG) and two patients with linear IgA disease were studied. In PG immune complexes containing IgGI and C3 were identified in six cases. In linear IgA disease IgAI containing immune complexes were found in both cases. Placentae from patients with PG showed aberrant expression of MHC Class II products. This was not seen in the placentae from patients with linear IgA disease. In PG there was incoordinate expression of the subregion products, DP and DR being more extensively and consistently expressed than DQ. These results and previous immunogenetic studies suggest that PG may be unique among organ specific autoimmune disease, the autoantibodies forming during an allogenic response rather than target cells behaving as antigen presenting cells.