Spontaneous and aggregated IgG induced rheumatoid factor producing cells in rheumatoid arthritis.

Seropositive rheumatoid arthritis (RA) patients were found to have high numbers of spontaneously occurring cells making rheumatoid factor (RF) reactive with human IgG as measured by a RF plaque forming cell (RF-PFC) assay. There was a significant positive correlation between the number of RF-PFC and both disease activity measured by the sedimentation rate and RF titer measured by the RA latex test. Aggregated IgG and pokeweed mitogen were equally effective stimulators of RF-PFC in cultures of RA peripheral blood mononuclear leukocytes. The rheumatoid ratio of helper (T4): suppressor (T8) T lymphocytes was also significantly increased over the ratio of normal controls, but this ratio did not correlate with the number of RF-PFC. Aggregated IgG or immune complexes may be responsible for stimulating RA RF-PFC in vivo.