Fc gamma R expression on macrophages is related to severity and chronicityof synovial inflammation and cartilage destruction during experimental immune-complex-mediated arthritis (ICA)

We investigated the role of Fc gamma receptors (Fc gamma Rs) on synovial ma crophages in immune-complex-mediated arthritis (ICA). ICA elicited in knee joints of C57BL/6 mice caused a short-lasting, florid inflammation and reve rsible loss of proteoglycans (PGs), moderate chondrocyte death, and minor e rosion of the cartilage. In contrast, when ICA was induced in knee joints o f Fc receptor (FcR) gamma -chain(-/-) C57BL/6 mice, which lack functional F c gamma RI and RIII, inflammation and cartilage destruction were prevented. When ICA was elicited in DBA/1 mice, a very severe, chronic inflammation w as observed, and significantly more chondrocyte death and cartilage erosion than in arthritic C57BL/6 mice. The synovial lining and peritoneal macroph ages of naive DBA/1 mice expressed a significantly higher level of FcgRs th an was seen in C57BL/6 mice. Moreover, elevated and prolonged expression of IL-1 was found after stimulation of these cells with immune complexes. Zym osan or streptococcal cell walls caused comparable inflammation and only mi ld cartilage destruction in all strains. We conclude that Fc gammaR express ion on synovial macrophages may be related to the severity of synovial infl ammation and cartilage destruction during ICA.