Modulation of lectinophagocytosis of Escherichia coli by variation of pH and temperature

The effect of variation of pH and temperature on the lectinophagocytosis of enteropathogenic Escherichia coli by polymorphonuclear leukocytes and macr ophages elicited by thioglycolate medium was evaluated. The phagocytosis of enteropathogenic E. coli is dependent on pH, being maximal at pH 7.0 and r educed at pH 5.5 or 6.0. Mannan and mannose las representative sugars that bind to phagocyte lectin receptors), are recognized by mannose receptors an d reduced the phagocytic index at pH 7.0 (from 41.6 +/- 8.5 to 17.0 +/- 6.1 ) and at pH 6.0 (from 24.1 +/- 5.1 to 14.5 +/- 5.0), suggesting that mannos e receptors, despite their reduced affinity for ligand at pH 6.0, also part icipate in phagocytosis of enteropathogenic E. coli. The inhibition of phag ocytosis by anti-substance A antibody was also examined at pH 7.0 and at pH 6.0, decreasing (from 41.6+/-8.5 to 21.1 +/- 3.4) and (from 24.1 +/- 5.1 t o 12.0 +/- 3.5), respectively. This antibody reduced the phagocytosis of en teropathogenic E. coli in phagocytic assays at 37 or 41 degrees C. These re sults suggest that the acidic pH decreased the affinity of mannose receptor s to ligands on the surface of E. coli and also affected the binding of lec tin from E. coli to N-acetylgalactosamine on phagocytes. (C) 1999 Federatio n of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.