Binding of microorganisms to the macrophage plasma membrane; effects of enzymes and periodate.

The nature of the binding of C. parvum organisms to the surface of glass-adherent mouse peritoneal exudate cells in vitro was studied using pretreatment of the cells with various enzymes and periodate. Trypsin, pronase, beta-galactosidase, phospholipases A, C and D and periodate all caused a decrease in binding to 40-60% of untreated control. Neuraminidase led to a 30% increase in binding. The binding ability returned to normal after 1 h at 37 degrees in culture medium following exposure to all the enzymes apart from pronase, which apparently could not be removed effectively by washing. The presence of EDTA in the medium inhibited recovery from treatment with trypsin and beta-galactosidase; return to normal after exposure to phospholipases A, C and D was slightly affected, whereas recovery from treatment with neuraminidase was unaffected. Cells that had been exposed to periodate did not regain normal binding ability after 1 h in tissue culture medium but the effect could be reversed chemically by treatment with borohydride. The role of different plasma membrane components in non-specific cellular recognition is discussed.