The Role of Cell Wall Carbohydrates in Binding of Microorganisms to Mouse Peritoneal Exudate Macrophages

The recognition by macrophages of unopsonized bacteria was studied, employing a binding assay, performed at 4 degrees C. Various Gram positive and Gram negative bacteria were shown to bind to glass-adherent mouse peritoneal exudate cells under these conditions, Str. pneumoniae being the only exception. The binding could be inhibited by pretreatment of the macrophage monolayers with various monosaccharides. The role of particular components of the bacterial cell wall in binding was examined further using different strains of K. aerogenes and S. typhimurium with a known cell wall composition and mutant strains deficient in certain sugars. The ability of a particular constituent to inhibit binding was found to correlate closely with its presence in the bacterial cell wall. It is concluded, that this form of binding, mediated by cell wall carbohydrates represents a primitive recognition mechanism enabling phagocytes to bind microorganisms.