Additionally, the number of KIR+CD8+ T cells was markedly increased in the kidneys of patients with SLE compared with healthy kidneys (Fig. 1C) and in the synovial tissues of rheumatoid arthritis (RA) patients compared with those with osteoarthritis (OA), which is not thought to be an autoimmune disease. Here, KIR3DL1 is linked to rheumatoid arthritis.