Findings from studies in humans support that IL-15 significantly enhances the cytotoxic effect of CD8+ T cells on target organs in the target tissues of patients with rheumatoid arthritis [241, 242], autoimmune myositis [243], obesity [244], celiac disease [245], and multiple sclerosis [246, 247], which is thought to be one of the mechanisms that leads to tissue destruction. The gene discussed is CD8A; the disease is multiple sclerosis.