Differential expression of macrophage effector functions: bactericidal versus tumoricidal activities.

Macrophage populations may be induced to express tumoricidal or bactericidal activities following exposure to certain stimuli. An understanding of the differences in the stimulatory mechanisms and in the characteristics of the macrophages they affect will be facilitated by comparing functional activities of various macrophage populations. The experiments described here were conducted to determine whether injection of a single stimulus necessarily drives cells to express both tumoricidal and bactericidal activities or whether selected reagents can drive cells to express one activity without expressing the other. The data show that a single population of mouse or hamster peritoneal exudate cells obtained following injection of proteose peptone is bactericidal for Listeria monocytogenes and for E. coli, but is not tumoricidal for TCMK-1, Ad2HE3, or mKS-A TU-5 target cells. In contrast, peritoneal exudate cells collected after injection of Bacillus Calmette Guerin (BCG) organisms are always highly tumoricidal, and either show no effect on Listeria monocytogenes or E. coli, or are at best bacteriostatic. Data indicate that the effector cells in these assays are macrophages, that the dissociation of tumoricidal and bactericidal activity occurs over a wide dose range, and that the tumoricidal capabilities are not artifacts of the assay system. These results suggest that a given macrophage population may preferentially express tumoricidal or bactericidal activities depending on the stimulus used.