IL-15 down-regulated CD62L expression on NK cells from healthy volunteers (38.1 ± 3.7% vs. 46.4 ± 3.4%, p < 0.001) as well as RA patients (28.5 ± 3.4 vs. 36.3 ± 3.5%, p = 0.001). The gene discussed is IL15; the disease is rheumatoid arthritis.