CX3CL1 and rheumatoid arthritis: CX3CL1 is expressed by macrophages and FLSCs in the synovial tissue of patients with rheumatoid arthritis and plays a critical role in animal models of arthritis (Blaschke et al., 2003; Nanki et al., 2002; Nanki et al., 2004; Ruth et al., 2001).