The Interaction of Opsonins with Human Polymorphonuclear Leucocytes (PMN). I. The Influence of Human Complement (C) and IgG on Ingestion and Digestion of C-Resistant E. coli

The influence of opsonization on ingestion and digestion of C-resistant E. coli was tested in a phagocytic system consisting of a monolayer of human PMN to which was added E. coli opsonized in different ways. At the end of the phagocytosis, noningested bacteria were separated and the monolayer was removed. The cells were then fractionated. The number of bacteria at different time intervals and the amount and distribution of lysosomal enzymes in the cell fractions were determined. It became apparent that the ingestion of cell-attached bacteria was independent of opsonins. However, the intracellular destruction was enhanced following opsonization with C only, although this was not the result of a greater discharge of lysosomal enzymes into the phagosome. We postulate that sublethal damage of E. coli by C renders the bacteria more sensitive to the bactericidal activity of the phagocytes.