Carbohydrates may play an important role in the interaction between phagocytic vesicles and lysosomes

Agglutination of phagocytic vesicles by plant lectins and lysosomes from guinea pig polymorphonuclear leukocytes (PMNs) were examined in vitro. PMNs were allowed to phagocytize paraffin oil emulsion, and phagocytic vesicles were isolated from the cells. First, the vesicles were suspended in isotonic sucrose or lactose with or without lectins, and then they were incubated at 0 degrees C for 20 min and photographed under a phase-contrast microscope. In sucrose, lectins such as Ricinus communis agglutinin, wheat germ agglutinin, Phaseolus vulgalis agglutinin-P and Ulex europeus agglutinin agglutinated the vesicles, while the vesicles without lectins remained dispersed. Concanavalin A agglutinated the vesicles in lactose solution, but the other lectins did not. These results suggest that the phagocytic vesicles have lectin receptors (carbohydrate moieties) on their cytoplasmic side, as galactosyl-, N-acetyl-galactosaminyl-, mannosyl-, glucosyl-, N-acetylglucosaminyl- and di-N-acetylchitobiose residues. Second, the phagocytic vesicles were incubated with lysosomes. Lysosomes induced agglutination of the vesicles immediately after incubation and this agglutination was inhibited by simultaneous addition of 50 mM mannose, fucose, N-acetylglucosamine, lactose and maltose, and 7 mM N-acetylneuraminic acid and 1.25 mg/ml fetuin. The results show that lysosomes agglutinated the phagocytic vesicles in vitro, and suggest that this interaction is mediated by recognition of the carbohydrate moieties on the vesicles.