Immunopathologic studies of rheumatoid arthritis. I. Absence of complement-dependent cytotoxicity of rheumatoid sera for rheumatoid synovial cell cultures.

A sensitive complement-dependent chromium release cytotoxicity assay was used to determine whether sera from rheumatoid arthritis (RA) patients contain antibody specific for an antigen on rheumatoid synovial cell cultures. Two hundred eight RA sera-RA synovial culture combinations were studied employing 21 sera and 16 synovial membranes; control combinations were derived from 5 normal sera and 10 degenerative joint disease synovial membranes. Anticomplementary activity of some rheumatoid sera was overcome using an increased complement concentration. The percent cytotoxicity of RA serum-RA culture combinations, both homologous and autologous, was not significantly greater than that of RA serum-control culture combinations. No correlation between duration of disease or duration of cell culture and percent cytotoxicity was found. Thus a unique antigen on cultured rheumatoid synovial cells was not recognized by rheumatoid serum antibody by use of this cytotoxicity assay.