Critical role of galectin-3 in phagocytosis by macrophages
Hideki Sano, … , Shozo Izui, Fu-Tong Liu
Hideki Sano, … , Shozo Izui, Fu-Tong Liu
Published August 1, 2003
Citation Information: J Clin Invest. 2003;112(3):389-397. https://doi.org/10.1172/JCI17592.
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Article Immunology

Critical role of galectin-3 in phagocytosis by macrophages

Abstract

Galectin-3 is a member of a large family of animal lectins. This protein is expressed abundantly by macrophages, but its function in this cell type is not well understood. We have studied the effect of galectin-3 gene targeting on phagocytosis, a major function of macrophages. Compared with wild-type macrophages, galectin-3–deficient (gal3–/–) cells exhibited reduced phagocytosis of IgG-opsonized erythrocytes and apoptotic thymocytes in vitro. In addition, gal3–/– mice showed attenuated phagocytic clearance of apoptotic thymocytes by peritoneal macrophages in vivo. These mice also exhibited reduced IgG-mediated phagocytosis of erythrocytes by Kupffer cells in a murine model of autoimmune hemolytic anemia. Additional experiments indicate that extracellular galectin-3 does not contribute appreciably to the phagocytosis-promoting function of this protein. Confocal microscopic analysis of macrophages containing phagocytosed erythrocytes revealed localization of galectin-3 in phagocytic cups and phagosomes. Furthermore, gal3–/– macrophages exhibited a lower degree of actin rearrangement upon Fcγ receptor crosslinkage. These results indicate that galectin-3 contributes to macrophage phagocytosis through an intracellular mechanism. Thus, galectin-3 may play an important role in both innate and adaptive immunity by contributing to phagocytic clearance of microorganisms and apoptotic cells.

Authors

Hideki Sano, Daniel K. Hsu, John R. Apgar, Lan Yu, Bhavya B. Sharma, Ichiro Kuwabara, Shozo Izui, Fu-Tong Liu

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Delayed phagocytosis of IgG-opsonized erythrocytes by gal3–/– macrophage...
Delayed phagocytosis of IgG-opsonized erythrocytes by gal3–/– macrophages in vitro. (a) After opsonized srbc’s were added to cultured BMMΦ at 4°C, synchronized phagocytosis was initiated by raising the temperature of the cultures to 37°C. After the indicated time periods, unbound srbc’s were removed and the cells were fixed for phase-contrast microscopy. (b) Phagocytic function was quantified by counting internalized srbc’s in more than 300 macrophages and the phagocytic index was calculated. Each data point represents the mean ± SD from five experiments. (c) Unsynchronized phagocytosis assays in BMMΦ were performed at 37°C for 20 minutes. Data are presented as mean ± SD from five high power fields and are representative of two experiments. P < 0.01 by Mann-Whitney U analysis between the genotypes. (d) Phagocytosis assays were performed as in a after staining of rbc’s with FITC-albumin at the time of opsonization. After 30 minutes, cells were harvested, washed, and subjected to flow cytometric analysis. Results shown are representative of six experiments.