The effect of antipolymorphonuclear leucocyte serum on Pseudomonas aeruginosa infection in rabbits

Studies were made on the rate of phagocytosis and killing of Pseudomonas aeruginosa by phagocytic cells in the peritoneal cavity of rabbits. In sublethal and lethal infections the phagocytosed bacteria were killed very quickly. In antibody-protected animals, the polymorphs became loaded with liveing bacteria, but this had little effect on the decline in infection. In sublethal infections and in protected animals theproportion of intracellular bacteria labelled with 32O or [14C]uracil was high and antibody greatly enhanced phagocytosis. In lethal infections the rate of phagocytosis was insufficient to prevent the development of a fatal septicaemia. Antipolymorphonuclear leucocyte serum (APS) completely suppressed the normal polymorph response to infection and greatly reduced resistance. The macrophages in the peritoneum, which were not affected by APS, delayed bacterial growth for several hours but were eventually unable to control bacterial mutiplication. The outcome of infection appeared to depend almost entirely on the ratio of bacterial to phagocytes and the presence of antibody. Iron-binding proteins probably make a significant contribution to resistance by reducing the rate of multiplication of extracellular bacteria.