Cytotoxicity of anti‐fab antibodies against b lymphocytes in rheumatoid arthritis

Abstract

Anti‐Fab antibody titers were positive in 70% of rheumatoid arthritis patients (54 of 77) and 3% (1 of 35) of healthy donors. Their specificity was examined by inhibition of the radioimmunoassay for anti‐Fab antibodies, which demonstrated that they are against the Fd region of the intact immunoglobulin molecule. In addition, anti‐Fab antibodies have broad specificities for IgG antigens, shown by inhibition with myeloma IgG. They are cytotoxic against B (20% of B cells from most healthy donors) but not T lymphocytes, with cytotoxicity greater at 5°C than 37°C. These studies show that the anti‐Fab antibodies interact with allotypic or idiotypic determinants on subpopulations of B lymphocyte cell surface antigens.