Thrombin inhibition ameliorates arthritis in C3/FcRγ-deficient K/BxN mice. K/BxN mice lacking C3 and FcRγ were treated with the thrombin inhibitor argatroban (filled circles) or vehicle control (open circles) from 3 to 6 weeks of age. Treatment was then stopped. The development of arthritis was determined by arthritis score (a) and twice weekly ankle measurements (b). Data plotted are mean ± standard error of the mean and represent seven or eight mice per group compiled from three independent experiments. *P < 0.05, **P < 0.005, ***P < 0.001. FcRγ, the cytoplasmic signaling chain shared by activating Fc receptors for immunoglobulin G.