Phagocytosis and Intracellular Killing of Staphylococcus Aureus by Human and Rabbit Blood Leukocytes

Abstract

Phagocytosis and intracellular killing of Staphylococcus aureus of the ordinary, nonencapsulated kind were examined in systems comprising blood and exudative leukocytes with autologous sera of normal and immunized rabbits, and also in systems comprising blood leukocytes with the autologous plasmas of infants during the first 9 months of life. In rabbit systems, phagocytosis measured during the first 30 min was reduced (level of significance, 90 to 93%) in the presence of heated serum in both normal and immunized rabbits when compared with that observed using fresh serum. Subsequent intracellular killing by blood leukocytes from normal rabbits in the presence of fresh and heated serum did not differ by amounts conventionally regarded as statistically significant. Intracellular killing by blood leukocytes was reduced in the presence of heated serum from rabbits immunized with staphage lysate and rabbits immunized with live staphylococci when compared with that observed in the presence of fresh serum. This was not the case in rabbits injected with heat-killed staphylococci. Plasmas and leukocytes from 11 infants in the first months of life, and in the last months of the 1st year of life, and from adults showed significant slowing in rate and amount of phagocytosis and no intracellular killing when plasma had been heat inactivated. The three infants 5 to 6 months of age showed only insignificant differences in phagocytosis and intracellular survival in fresh as compared with heat-inactivated plasma. In these respects the plasmas of the 5- to 6-months-old infants behaved like the sera of normal rabbits; all other plasmas and the plasmas of adult humans behaved like the sera of immunized rabbits.