IL-15 is one of the crucial cytokines in rheumatoid arthritis pathogenesis.483,484 Its function primarily involves stimulating the differentiation and proliferation of T cells and natural killer cells.485 During the pathogenesis of OA, elevated IL-15 concentrations in synovial fluid at early disease stages stimulate secretion of specific MMP-group metalloproteinases.486. This evidence concerns the gene IL15 and rheumatoid arthritis.