Determination of the bacteriostatic capacity of neutrophils and monocytes in mixed cell populations

Cline [1, 2] described a method of determining the phagocytic and bacteriostatic activity of individual types of leukocytes within mixed cell populations. We tried to improve the applicability of this method for the investigation of clinical problems.--Bacteria in the log-phase of growth were incubated in test tubes with leukocytes separated from venous blood. After a short period of phagocytosis 3H-thymidine was added to label DNA-synthesizing organisms. Smears were prepared and processed by autoradiography. The labeling indices of extracellular bacteria and of those phagocytized by neutrophils and monocytes were determined microscopically. The intracellular inhibition of DNA-synthesis was taken as indicative of the bacteriostatic activity of the leukocytes. The proposed modification of Cline's assay is suited to investigate clinical problems of phagocyte dysfunction.