Serum and blister fluid immune complexes in bullous pemphigoid: detection with C1q and monoclonal rheumatoid factor.

Eighty serum samples and 24 blister fluids from 51 patients with active bullous pemphigoid were tested for the presence of immune complexes by both a monoclonal rheumatoid factor (mRF) inhibition radioassay and Li Clq-binding radioassay. Forty-two of the SO serum samples were positive by the mRF assay, while 27 were positive by the C Iq-binding assay. Antibody titres to the basement membrane zone did not correlate with levels of circulating immune complexes. Thirteen of 24 blister fluids had detectable immune complexes by the Clq assay, while only seven of 24 blister fluids were positive by the mRF assay. Sucrose density-gradient ultracentrifugation studies suggest that the mRF- and Clq-reactive substances in both bullous pemphigoid sera and blister fluids are ofa size compatible with immune complexes. Although immune complexes tire detectable in a high percentage of bullous pemphigoid patients, their role in this disease may be epiphenomenal rather than pathogenetic. merely reflecting the presence of autoantibody and soluble antigen. [ABSTRACT FROM AUTHOR]