differential production of igm a nd iga rheu matoid factors in peripheral blood and synovium of patients with rheumatoid a rthritis

total igm, iga, and igm-rheumatoid factor (rf) and iga-rf were quantitated in the serum and synovial fluid of 35 seropositive and 8 seronegative rheumatoid arthritis (ra) patients, using a sensitive enzyme-linked immunosorbent assay (elisa). mononuclear cells isolated from peripheral blood and synovial fluid of three seropositive patients were also stimulated in vitro with phorbol myristate acetate (pma) and culture supernatants collected for measurement of total immunoglobulin (lg) and rf. our results demonstrated that as a proportion of total ig, igm-rf and iga-rf were significantly higher in the synovial fluid of seropositive patients compared to their serum level. similar results were observed for in vitro stimulated culture supernatants from the same patients. this difference, however, was not evident in the seronegative group of patients. these results indicate that synovium could be considered as the original site of rf production in seropositive ra patients, and that different repertoires of blymphocytes may be involved in rf production in peripheral blood and synovial tissues of affected joints.