The influence of high and low pressure on phagocytosis of Escherichia coli by human neutrophils in vitro.

Human polymorphonuclear neutrophils were exposed to high (4 atm) and low (0.4 atm) pressures in vitro before and during phagocytosis of radiolabelled Escherichia coli. Preexposure of the neutrophils to high pressure before phagocytosis did not influence uptake. However, when phagocytosis took place at 4 atm the uptake of bacteria opsonized by active serum and IgG was significantly depressed. On the other hand, uptake in the presence of heat-inactivated serum or albumin and uptake of non-opsonized E. coli was not changed at high pressure. The results suggest an influence on uptake mechanisms related to receptors in the cell membrane. When the neutrophils were exposed to hypobaric pressure both before and during phagocytosis, the uptake of nonopsonized E. coli was slightly depressed. However, neither preexposure nor exposure during phagocytosis was sufficient alone to elicit this inhibiting effect. The uptake of E. coli opsonized by active serum or IgG was not influenced by low pressure.