To examine whether a cytokine, autocrine motility factor (AMF), plays a role in rheumatoid arthritis (RA).
We investigated the chemokinetic activity of synovial fluids (SF) obtained from patients using a unique protein-free culture fibrosarcoma Gc-4 PF, the motility of which is specifically dependent on the cytokine.
Treatment of the cells with the SF stimulated their phagokinetic motility by 1.4, 1.8, and 2.1-fold at protein concentrations of 100, 250 and 500 micrograms/ml, respectively. This dose dependent response was observed in all 3 patients with classical or definite RA. In contrast with Gc-4 PF cells, the SF did not stimulate the motility of Gc-4 SD cells that have little response to AMF. The ability of this chemokinetic activity to block binding of the monoclonal antibody to the receptor for AMF was demonstrated on immunoblots.
Based on these results, it is suggested that the motile activity may be AMF. The possible role of the cytokine in the pathogenesis of RA is discussed.