However, because IL-7 can stimulate cells to produce additional cytokines, such as IL-6, IL-8 and TNF-α [10] and (as shown here) can stimulate additional production of MMP-13 when combined with IL-1β, it may be an important contributor to joint tissue destruction in OA and RA. The gene discussed is CXCL8; the disease is rheumatoid arthritis.