Detection of basement membrane zone antigens and C3 fragments in the blister fluid of bullous pemphigoid.

In polyacrylamide gel gradient electrophoresis, serum and blister fluid of patients with bullous pemphigoid showed a nearly identical protein distribution pattern except for one more concentrated fraction in the blister fluid. This fraction could be isolated by several gel chromatographic steps and then be characterized as a protein with a molecular weight of 240,000 (BFP 240,000) consisting of several subunits. Two of these subunits could be identified as C3 fragments and two other ones as basement membrane zone antigens (BMZ-Ag) by means of a modified Laurell technique. The molecular weight of the BFP 240,000 may be small enough to allow it to penetrate through the vessel wall into the blood circulation where, with the BMZ-antibodies (BMZ-Ag-BMZ-Ab-complexes can be formed. The occurrence of such immune complexes in the serum has been shown in a previous paper.