Decreased IgG production but increased MIP-1β expression in collagen-induced arthritis in C-C chemokine receptor 5-deficient mice

Collagen-induced arthritis (CIA) is a widely used model of human rheumatoid arthritis (RA) characterized by chronic inflammation of the synovial joints. The pathogenesis of RA and CIA has not been completely defined, but both involve the recruitment of leukocytes and lymphocytes to the joints and Th1-type cell mediated autoimmune responses. The C-C chemokine receptor 5 (CCR5) is preferentially expressed on Th1 cells and has been strongly implicated in inflammatory process through trafficking of leukocytes and lymphocytes into the sites of inflammation. We investigated the role of the CCR5 in CIA using CCR5 knockout mice (CCR5−/−) in which we analyzed the consequences of CCR5 deficiency for the immune response and inflammation. We found that CCR5−/− mice showed a significant reduction in the incidence of CIA after collagen II (CII)-immunization as compared to wild-type (CCR5+/+) mice. The reduced incidence seen in CCR5−/− mice was associated with these animals having significantly lower IgG levels, especially IgG2a and IgG2b antibodies against CII, as well as an obviously augmented IL-10 production in splenocytes. Overproduction of MIP-1β in CCR5-deficient mice after CII-immunization may contribute partially to the occurrence of arthritis.