Induction and suppression of collagen-induced arthritis is dependent on distinct Fc gamma receptors

Receptors for immunoglobulin (Ig)G (Fc gamma Rs) are important for the anti body-mediated effector functions of the immune system. Fc gamma RI and Fc g amma RIII trigger cell activation through a common gamma chain, whereas Fc gamma RII acts as a negative regulator of antibody production and immune co mplex-triggered activation. Here we describe the in vivo consequences of Fc gamma R deficiency in a mouse model of human rheumatoid arthritis. FcR gam ma chain-deficient mice on arthritis-susceptible DBA/1 background were immu nized with collagen for induction of collagen-induced arthritis. The DBA/1 mice lacking FcR gamma chain were protected from collagen-induced arthritis in contrast to wild-type mice, although both groups produced similar level s of IgG anticollagen antibodies. In comparison, DBA/1 mice lacking Fc gamm a RII developed an augmented IgG anticollagen response and arthritis. These observations suggest a crucial role of Fc gamma RI and Fc gamma RIII in tr iggering autoimmune arthritis.