Quantification by ELISA of cytokines IL-15Ralpha, IL-15, IL-6, and TNFalpha in synovial fluids from the knee joints of 30 RA and 29 OA patients, showed that SF from RA patients contained significantly higher concentrations of IL-15Ralpha (p = 0.03, Figure 1A), TNFalpha (p = 0.002, Figure 1C) and IL-6 (p = 0.001, Figure 1D) than the OA group, but in the case of IL-15 we did not find any significant difference between RA and OA groups (p = 0.29) (Figure 1B). This evidence concerns the gene IL15 and rheumatoid arthritis.