Inhibition of human leukocyte migration inhibitory factor (LIF) by alpha-L-fucose

Peak leukocyte migration inhibitory activity was produced in vitro by human lymphocytes stimulated with concanavalin A and eluted from Sephadex G-100 gel columns in fractions containing molecules of mol. wt. 40,000-50,000 daltons. No activity was found in fractions containing molecules of mol. wt. 23,000 daltons which is the estimated size of the human macrophage migration inhibitory factor (MIF). In the present experiments migration inhibition was tested on human peripheral blood leukocytes migrating under agarose. Unconcentrated supernatant activity was reduced in a dose-related manner by alpha-L-fucose. At a concentration of 0.1 M alpha-L-fucose, the mediator activity was completely neutralized. The effect was reversible and specific for alpha-L-fucose. Concentrated supernatant activity, however, was only slightly reduced even in the presence of a higher concentration of sugar. The possible role of alpha-L-fucose as a part of a mediator receptor on the indicator cells is discussed.