INTERACTION OF MACROPHAGE-MIGRATION-INHIBITORY FACTOR WITH HEMATIN

Macrophage-migration-inhibitory factor (MIF) is retained by S-hexylglu tathione-agarose but is not specifically eluted in high yield. Human l iver 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) Mel. Med. 2, 143-149], The L-dopachrome methyl ester tautomerase activity of human liver MIF was not inhibited by a variety of glutath ione S-conjugates, eicosanoids or glucocorticoids but was very sensiti ve to inhibition by haematin (IC50 100-200 nM). The inhibition was non -competitive and showed positive co-operativity (h = 5.8). Similar sen sitivity 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 modulati ng the function of MIF in the initiation of immune responses.