Interaction of macrophage-migration-inhibitory factor with haematin

Macrophage-migration-inhibitory factor (MIF) is retained by S-hexylglutathione-agarose but is not specifically eluted in high yield. Human liver MIF was purified in high yield using retention by phenyl-agarose at low ionic strength and cation-exchange FPLC as described for bovine lens MIF [Rosengren, Bucala, Aman, Jacobsson, Odh, Metz and Rorsman (1996) Mol. Med. 2, 143-149]. The l-dopachrome methyl ester tautomerase activity of human liver MIF was not inhibited by a variety of glutathione S-conjugates, eicosanoids or glucocorticoids but was very sensitive to inhibition by haematin (IC50 100-200 nM). The inhibition was non-competitive and showed positive co-operativity (h=5.8). Similar sensitivity to haematin was obtained with purified recombinant human MIF. The sensitivity of MIF to haematin is approx. 1000-fold greater than for any previously described ligands, and is within its physiological range. Therefore the interaction is likely to be important in modulating the function of MIF in the initiation of immune responses.