Monocyte fc receptor function in rheumatoid arthritis. enhanced cell‐binding of igg induced by rheumatoid factors

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Abstract
Monocytes from 11 patients with rheumatoid arthritis and 10 control subjects were purified by countercurrent elutriation. Rheumatoid arthritis monocytes had more cell‐associated IgG (P < 0.001) and bound more 125I‐labeled heat‐aggregated IgG in vitro (P < 0.02) than did monocytes from control subjects. Interaction of rheumatoid factor (RF) with monocytes was then investigated. Purified 125I‐labeled IgM‐RF and IgG‐RF bound directly to monocytes from normal individuals. Furthermore, preincubation of normal monocytes with RF augmented subsequent binding of aggregated IgG to the cells. We conclude that monocyte‐associated RF can enhance binding of IgG‐containing immune complexes to the cells and can exaggerate the measured number of Fc receptors. Such cell‐bound RF may affect clearance of immune complexes by the reticuloendothelial system in vivo.