CCR1 and Arthritis: The expression of CCR1 has been shown to be increased in synovial tissue of patients with RA (16–18) and in animal models of arthritis (19); deficiency of CCR1 has been shown in animal models to limit the development of arthritis and other experimental models of inflammatory disease, but blockade of CCR1 has been trialed in RA with only limited success (20, 21).