INHIBITION OF PHAGOCYTIC-ACTIVITY BY THE N-ACETYL-D-GALACTOSAMINE-SPECIFIC LECTIN FROM AMARANTHUS-LEUCOCARPUS

Amaranthus leucocarpus lectin (ALL), specific for N-acetyl-D-galactosa mine, induces inhibition of the erythrophagocytic activity of resident murine peritoneal macrophages and of the macrophage-like cell line J- 774. This effect was observed only in macrophages that were Mac-2 (CD1 1c/CD18 or CR4) negative, indicating that macrophage activation induce s important modification to the glycosylation (mainly O-glycosylation) of the membrane. Receptors for IgM and C3b remain unaltered after lec tin treatment. Ultrastructural analysis revealed (a) that ALL induced the formation of pinocytic vacuoles, and (b) a regular distribution ov er the macrophage membrane as well as endosomal vesicles of the gold l abeled ALL. Our results suggest that macrophage membrane glycoproteins with constitutive N-acetyl-D-galactosamine residues participate in th e regulation of pinocytic-phagocytic vacuole formation.