MORPHOLOGICAL STUDY OF THE IN VITRO CYTOTOXIC EFFECT OF α‐HEMOLYTIC E. COLI BACTERIA AND CULTURE SUPERNATANTS ON HUMAN BLOOD GRANULOCYTES AND MONOCYTES

Abstract

The morphological changes of human blood granulocytes and monocytes caused in vitro by α‐hemolytic strains of E. coli and bacteria‐free culture supernatants of these bacteria were studied by light‐ and transmission electron microscopy. The following sequence of cellular alterations were observed: Cessation of intracellular cytoplasmic streaming and cellular movements succeeded by extension of cytoplasmic pseudopodia, degranulation and development of cytoplasmic and nuclear edema. Within two hours the leukocytes appeared as empty sacks. Finally, long straight filaments were formed between the cells. The changes induced by α‐hemolytic bacteria and culture supernatants containing free α‐hemolysin appeared to be identical. The cytotoxic effect became more pronounced as the numbers of bacteria, the hemolytic activity of growth supernatants or the period of incubation were increased. A β‐hemolytic and a non‐hemolytic E. coli strain were not cytotoxic.

IN VITRO CYTOTOXIC EFFECT OF α‐HEMOLYTIC AND NONHEMOLYTIC ESCHERICHIA COLI ON HUMAN BLOOD GRANULOCYTES AND MONOCYTES

“…Fractionation of blood leukocytes. Blood was collected from healthy adults and suspensions of mononuclear cells and purified granulocytes were prepared as described earlier (10). Plasma was centrifuged and filtered to remove platelets.…”

“…Qzranfitative test for a-hemolysin. The I5 strains used for detail studies were tested as described earlier (10).…”

“…It has been reported that bacterial culture supernatants containing free E. coli a-hemolysin and partially purified E. coli a-hemolysin is cytotoxic to rabbit and human leukocytes and impedes the functions of these cells in vitro in serum-free media (2,3,6,17). We have previously demonstrated that a-hemolytic E. coli may be cytotoxic to human phagocytic blood cells in the presence of fresh autologous plasma (8,9,10). In screening a large number of strains we found that about half the a-hemolytic strains were cytotoxic and cytolytic to varying degrees, whereas none of the nonhemolytic strains caused cell damage (9).…”