The role of TNF-α in JIA is suggested by the findings of high TNF-α levels in the synovial fluids of these patients [69], from studies on transgenic mice overexpressing TNF-α and developing a polyarthritis [70], and from the observation of a positive response to anti-TNF-α biologic drugs in arthritis patients [71–73]. The gene discussed is TNF; the disease is juvenile idiopathic arthritis.