NMUR1 and NMUR2 are dispensable for the induction of autoantibody-mediated arthritis. Serum from K/BxN mice was injected into mice lacking NMUR1, NMUR2, both NMUR1 and NMUR2, or littermate controls animals on days 0 and 2. The development of arthritis was assessed by determination of (A) arthritis score and (B) ankle thickening. Data plotted are means ± SEM and are compiled from four experiments with eight to fourteen animals per genotype. For arthritis score (A), there were no statistical differences between the four groups. For ankle thickening (B), ankle thickening scores increased slightly more rapidly in the NMUR1-/- mice relative to the control mice (P = 0.042) and relative to the NMUR2-/- mice (P = 0.015). There were no statistically significant differences between the other groups of mice (repeated-measures analysis of variance followed by post-hoc Tukey's multiple comparison test). SEM: standard error of the mean.