p38αβ^Y323F mice are less susceptible to CIA than WT mice. WT (n = 4) and p38αβ^Y323F (n = 5) mice were immunized with bovine type II collagen in CFA and 3 weeks later boosted with collagen in Incomplete Freund Adjuvant. (A) Representative images of limbs of WT animals that developed ankylosis, and p38αβ^Y323F mice that developed only mild swelling. (B) The clinical scores are shown over time. These data are representative of 2 independent experiments. (C) The percentage of mice that developed ankylosis in 2 independent experiments: WT, n = 9; p38αβ^Y323F, n = 8.