Human MIF is a 12.5 kDa, 115 amino acid (aa) nonglycosylated polypeptide that is synthesized without asignal sequence .Secretion occurs nonclassically via an ABCA1 transporter.Pro-inflammatory cytokine.Involved in the innate immune response to bacterial pathogens. The expression of MIF at sites ofinflammation suggests a role as mediator in regulating the function of acrophages in host defense.Counteracts the anti-inflammatory activity of glucocorticoids. Has phenylpyruvate tautomerase anddopachrome tautomerase activity (in vitro), but the physiological substrate is not known. It is not clearwhether the tautomerase activity has any physiological relevance, and whether it is important for cytokineactivity.