CD80 and rheumatoid arthritis: In the case of rheumatoid arthritis (RA) pathogenesis, the critical role of the adaptive immune response and proinflammatory cytokines has been unequivocally established by the efficacy of marketed biologics targeting tumor necrosis factor (TNF) alpha, interleukin (IL)-6, CD20 (B-cell depletion) and CD80/86 (modulation of T-cell co-stimulation).