NCR1 and rheumatoid arthritis: To elaborate further, among the activating receptors, subjects with RA showed a reduced NKp46 expression on NK cells compared to healthy volunteers, and its expression on NK cells obtained from both patients with RA and healthy controls was modulated by IL-15; no differences in CD69 expression were revealed among the two groups, but defective response to exogenous IL-15 was observed in the former.