IL15 and rheumatoid arthritis: In recently diagnosed seropositive RA, NK cells from blood showed decreased IFN-γ expression (39), while NK cells from blood in deformative RA secrete more IFN-γ upon exposure to IL-2 compared with healthy blood, and synovial fluid NK cells from deformative RA secrete more IFN-γ stimulated with IL-2 or IL-15 than non-deformative RA (17).