Finally, since B cells or some B cell subpopulations play crucial roles in the development of rheumatoid arthritis (RA) in humans and of collagen-induced arthritis (CIA) in mice (21–25), we employed CIA as a model to evaluate the role of Tespa1 in B cell-associated autoimmune diseases, and found that Tespa1-deficient chimeras showed a lower incidence and clinical disease severity index of autoimmune arthritis. The gene discussed is TESPA1; the disease is rheumatoid arthritis.