However, the role of IL-15R-independent membrane-bound IL-15 in RA has not been completely studied until now, and no data has been reported so far concerning the existence of natural sIL-15Rα in synovial fluid of RA patients, two elements necessary to induce proinflammatory cytokines through reverse signaling that could contribute to pathogenesis of RA. Here, IL15 is linked to rheumatoid arthritis.