Human macrophage migration inhibitory factor (MIF) is a 12.5 kD, 115 amino acid, non-glycosylated polypeptide expressed by multiple cell types, including activated T cells, macrophages, eosinophils, epithelial cells, and endothelial cells. MIF plays many roles in biological processes such as catalytic activity, immunity, endocrine regulation, signal modulation, and inflammation. MIF is expressed in malignant cells including lung, liver, breast, colon, and prostate tumors. Studies suggest that MIF might serve as a molecular link between chronic inflammation and cancer. Recombinant MIF consists of a mixture of monomers, dimers, and trimers. The physiologically active forms are believed to be predominantly dimeric and trimeric forms.