Fusion of macrophages on an implant surface is associated with down-regulated expression of ligands for galectin-1 and -3 in the rat.

Galectins have a wide range of biological activities which are elicited by binding to appropriate glycoligands. Besides regulation of the expression of the galectins the extent of the presence of suitable binding sites will be relevant to infer the cellular responsiveness to this class of sugar receptors. Thus ligand presentation requires monitoring by the tissue lectin. We demonstrate the expression of galectin-3 by macrophages and foreign-body giant multinucleate cells colonizing a cellophane implant in the rat by the A1D6 monoclonal antibody. The extents of ligand presence are visualized in the same cells by biotinylated galectin-3 and also by galectin-1 which is produced by diverse mammalian cell types and widely distributed. Labeled mistletoe (VAA) and tomato (LEA) lectins are used as tools to assess the degree of similarity of the binding profile between endogenous and exogenous proteins. The presentation of alpha-galactosides is monitored with a natural immunoglobulin G subfraction obtained by two consecutive affinity chromatography steps. The binding of labeled galectins and plant lectins was significantly lower to foreign-body giant multinucleate cells than to mononuclear macrophages. The application of the alpha-galactoside-specific probe yielded no significant staining. The potential problem of epitope accessibility could be excluded by the concomitant positivity obtained with an IgG subfraction with selectivity to beta-galactosides also obtained by affinity chromatography. These results provide no evidence for a role of alpha-galactosides for the binding of galectins in the rat macrophages colonizing the implant. The reduced level of expression of glycoligands for galectin-1 and -3 in foreign-body giant multinucleate cells in contrast with the mononuclear macrophages suggests an inhibitory influence of macrophage fusion on the expression of galectin-reactive molecules.

Effect of phagocytosis of pHEMA particles and of heat-killed Candida albicans on expression of carbohydrate-binding sites such as endogenous lectins in phagocytes.

Phagocytosis of particles is an integral part of the defence system. Besides clearing the environment of foreign material this mechanism may affect the expression of physiologically relevant epitopes such as carbohydrate-binding sites, e.g. lectins. To determine the effect of particle design on the expression of such determinants in human monocytes and peritoneal macrophages either in suspension or after adherence, the binding of labelled (neo)glycoproteins was comparatively studied after exposure to poly (2-hydroxyethyl methacrylate) particles and heat-inactivated Candida albicans cells. A stimulatory effect of phagocytosis on extent of expression of binding sites for (neo)glycoproteins in phagocytic cells was observed. The levels of responsiveness varied according to the type of particle, adherence of the cell adding a further regulatory parameter. These results support the notion of a potential influence of the chemical structure and/or the form of an engulfed particle on phagocyte differentiation.