Difference in Binding of Killed and Live Streptococcus pneumoniae Serotypes by C-Reactive Protein

The binding and opsonic properties of C-reactive protein (CRP) for various species of bacteria were investigated. CRP bound more avidly to killed than to live Streptococcus pneumoniae , the binding varying among various serotypes; CRP hardly bound to a number of other bacterial species studied. CRP enhanced complement-dependent phagocytosis of live S. pneumoniae by granulocytes but did not enhance the phagocytosis of live Staphylococcus aureus or group B streptococci. We suppose that CRP may serve as an opsonin for killed bacteria and bacterial debris but is probably not an important opsonin for live bacteria other than S. pneumoniae .     

Method to Prove Ingestion of Particles by Macrophages with Light Microscopy

Research on phagocytosis is often hampered by the inability to distinguish whether (opsonized) particles have been ingested by phagocytes or are only attached to the surface of these cells. Treatment of the cells after phagocytosis to remove all extracellular particles makes it possible to evaluate phagocytosis with certainty by light microscopy. Opsonized erythrocytes attached to the macrophage surface are usually removed by hypotonic lysis. The present report describes the advantages of the use of lysostaphin to lyse Staphylococcus aureus and of xylene, chloroform or dioxane to dissolve polystyrene latex beads on the surface of peritoneal macrophages and embryonic fibroblasts. This procedure facilitates differentiation between professional and facultative phagocytes.     

Kinetics of Phagocytosis and Intracellular Killing of Staphytococcus aureus and Escherichia coli by Human Monocytes

Tie kinetic patterns of the phagocytosis and intracellular killing of Staphytococcus and Echerichia coli by monocytes were investigated separately to acquire more insight into the total process, i.e. from the ingestion to the death of the micro-organisms. Phagocytosis proved to be dependent on: (1) both the bacteria-to-monocyte ratio and the monocyte concentration; a concentration of at least 5 × 10⁵ monocytes/ml proved necessary for the measurement of ingestion, whereas the rate of ingestion was found to be proportional to the number of extracellular bacteria until a maximum rate is reached, (2) the serum concentration in the incubation medium, which influenced both the rate of phagocytosis and the maximum number of bacteria taken up by one monocyte, and (3) the temperature, the highest rate of phagocytosis being reached at 37–41°C The intracellular killing proved to be dependent on: (1) the number of bacteria ingested; the rate of killing was proportional to the number of ingested bacteria until a maximum rate was reached; (2) the temperature, since a maximum rate of killing is only reached at 37–41°C: at tower and higher temperatures the rate of killing is lower, in the latter case due to inactivation of extracellular stimuli. These separate data on the ingestion and killing processes made it possible to compute the theoretical numbers of extracellular, viable intracellular, and total intracellular bacteria for a model system consisting of 5×10⁶ monocytes, 5×10⁶ bacteria, and 10% serum. These calculated values are in agreement with the experimental data.