The C1q binding assay and the nephelometric monoclonal rheumatoid factor assay were able to discriminate 79% and 57% respectively of rheumatoid arthritis (RA) patients from healthy blood donors. In addition these assays could distinguish those patients with active arthritis from those with inactive disease, and the C1q binding assay correlated significantly with other laboratory indices of the ...

Complement-mediated lysis of sheep erythrocytes coated with optimal concentrations of rabbit IgG hemolysin was inhibited by euglobulin fractions from the sera of patients with seropositive rheumatoid arthritis. That this was due to direct interaction with the IgG coat on the red cell rather than a nonspecific reaction with complement in the fluid phase was confirmed by controls using cells coat...