SOME PHYSICOCHEMICAL PROPERTIES OF HUMAN LEUCOCYTE MIGRATION INHIBITORY FACTOR (LIF)

Abstract

Leukocyte migration inhibitory factor (LIF) obtained from human lymphocytes stimulated with concanavalin A was consistently and irreversibly blocked by the serine-esterase inhibitor phenyl-methyl sulfonylfluoride (PMSF). This effect was not due to F ions, hydrolysis products of PMSF or to impurities. PMSF pulse treatment of human buffy coat cells did not affect cell migration under agarose. LIF was also irreversibly destroyed by treatment with L-cysteine and 2-mercaptoethanol, suggesting that the molecule contains disulfide linkage groups decisive for its configuration and biological activity. Disodium EDTA completely inhibited LIF activity, but only if present during the entire migration period. Removal of EDTA before LIF assay restored LIF activity. Leukocyte migration was neither influenced by L-cysteine nor by EDTA. LIF activity was slightly diminished after treatment at 56.degree. C for 1 h and completely lost activity at 80.degree. C for 1/2 h. LIF appeared rather stable when treated at pH values between 4 and 11. These findings suggest an esterase or a protease nature for human LIF.