Mice lacking all known NMU receptors remain susceptible to autoantibody-mediated arthritis. Serum from K/BxN mice was injected into mice lacking NTSR1 or mice lacking NMUR1, NMUR2, and NTSR1 on days 0 and 2 (100 μL/injection). The development of arthritis was assessed by determination of (A) arthritis score and (B) ankle thickening. Data plotted are means ± SEM and represent one of three independent experiments with a total of eight to fifteen mice per group. There were no statistically significant differences between the groups (repeated-measures analysis of variance followed by post-hoc Tukey's multiple comparison test). NMU: neuromedin U; SEM: standard error of the mean.