Uptake of non-opsonized E. coli by unstimulated mouse peritoneal macrophages

A method is described for the study of phagocytosis of 32P-labelled, non-opsonized, viable E. coli by mouse peritoneal macrophages. Factors influencing the uptake, such as medium, number of bacteria and time of phagocytosis, were standardized. The kinetics of the uptake were studied by visual counting of bacteria and by measuring the distribution of radioactive labelling. The uptake of 32P by the macrophages is well correlated to the number of bacteria phagocytized. The amount of phagocytosis depends on the bacterial density of the medium and the time of phagocytosis. When the medium contains more than 10(9) bacteria per ml, the maximum phagocytic capacity is reached after 90 minutes.