Binding characteristics of fluoresceinated lotustetragonolobus fucolectin to macrophage populations which are either responsive or refractory to activation by lymphokine

Abstract

Fucose binding protein (FBP) from Lotus tetragonolobus seed was studied by fluorescencemicroscopy for its binding characteristics to various guinea pig peritoneal macrophage populations. Fluoresceinated FBP (FITC-FBP) was bound optimally at 22°C in a punctate distribution and was internalized at 37°C. Binding of FBP to macrophages was reversed specifically by the competitive sugar L-fucose, and not by D-fucose, L-rhamnose, or D-galactose. FBP was bound with greater frequency and intensity to 3-day oil-elicited peritoneal macrophages which are responsive to migration inhibition by FBP and migration inhibitory factor (MIF) than to resident or 7-day inflammatory macrophages which are unresponsive to activation by the same effectors. Competition for visual binding of FITC-FBP to macrophages was demonstrated by preincubation of cells with unlabeled FBP or MIF. Competition of FITC-FBP binding by MIF was reversed by L-fucose. These results indicate that FBP binds preferentially, with greater frequency and intensity, to macrophage subpopulations which are responsive to MIF than to MIF-refractory macrophages. The data further supports the existence of a common receptor site for MIF and FBP on the macrophage membrane which involves fucosyl determinants.