IL17RA and arthritic joint disease: As previously described [25], compared to WT mice, IL-17R −/− mice had reduced synovial hypercellularity leading to significantly decreased macroscopic arthritis severity scores (Figure 7A, mean ± SEM score 1.5±0.17 in WT versus 0.31±0.10 in IL-17R −/− mice; P<0.05).