The Molecular Complex of Macrophage Migration Inhibitory Activity (MIF) and its Role in Inflammatory Reactions

The macrophage migration inhibitory factor (MIF), the first lymphokine ever to be described (1, 2) is released by cultivated lymph node, spleen or peripheral blood mononuclear cells upon antigen or mitogen stimulation. As its production is related to the state of immunity, MIF was considered to be a molecular equivalent of the delayed type hypersensitive (DTH) state. By chemical characterization it became clear that MIF activity was associated with a group of molecules, whose molecular weight ranged from below 10,000 to greater than 60,000 D. Biological activity was found after isoelectric focussing at a pH of 5 and 3. The data obtained were similar with MIF from mitogen-stimulated mouse, guinea pig and human peripheral blood mononuclear cells (3).