On the functional level, MIF is involved in a variety of biological functions including the production of inflammatory cytokines, such as tumor necrosis factor, interleukin-6, interferon-γ, and interleukin-1β; hormone immunomodulation; muscle glucose catabolism regulation; tumor growth promotion; and pathology of diseases such as rheumatoid arthritis, asthma, lupus, and atherosclerosis (5). Here, MIF is linked to rheumatoid arthritis.