To examine the role of endogenous SIGIRR during inflammation in vivo, we investigated the clinical and histopathological features of SIGIRR-deficient C57BL/6 mice in a mouse model of antigen-induced arthritis (AIA) with mBSA as an antigen, which shares both immunological and pathological features with human rheumatoid arthritis. This evidence concerns the gene SIGIRR and rheumatoid arthritis.