Antibody‐Binding to the 180‐kD Bullous Pemphigoid Antigens at the Lateral Cell Surface Causes Their Internalization and Inhibits Their Assembly at the Basal Cell Surface in Cultured Keratinocytes

We demonstrated the effects of monoclonal antibodies to the 180‐kD and 230‐kD BP antigens (BPA) and of BP sera on Ca++‐induced formation of hemidesmosomes in cultured human keratinocytes (a cell line, DJM‐1) by immunofluorescence microscopy. Under low Ca++ (0.07 mM) conditions, the 180‐kD and 230‐kD BPAs were distributed homogeneously on the basal plasma membrane, while they formed a peculiar concentric ring or arch (ring/arch) arrangement in high‐Ca++ (1.87 mM) medium. On the other hand, the apical‐lateral cell membrane was stained homogeneously with antibodies to the 180‐kD BPA, but not to the 230‐kD BPA, both in low and high Ca++ media. The low‐high Ca++ switch at first caused disappearance of the antigen from the basal plasma membrane and then formed the high‐Ca++ ring/arch pattern within 3 hrs. In this system, monoclonal antibodies to the 180‐kD and 230‐kD BPAs and the sera from 5 BP patients, 2 pemphigus vulgaris (PV) patients, and 4 normal volunteers were added into the culture media. The addition of anti‐180‐kD BPA antibodies or any BP serum caused the internalization of the 180‐kD BPA from the apical‐lateral cell membrane and inhibited the Ca++‐induced formation of the ring/arch pattern on the basal membrane, possibly by inhibiting the movement of the antigen from the lateral to the basal membrane to form hemidesmosomes. The internalized fluorescence dots were shown to be composed of the 180‐kD BPA and patient's IgG, but not of the 230‐kD BPA by double‐immunostaining, suggesting the internalized 180‐kD BPA was from the apical‐lateral membrane, but not from hemidesmosomes. Monoclonal antibodies to the 230‐kD BPA and normal and PV sera did not cause these effects. These results suggest that autoantibodies to the 180‐kD BPA, but not to the 230‐kD BPA, may directly bind the antigen on the cell surface and disturb the formation of hemidesmosomes.