Effect of cortisone on the macrophages of different species of animal.

Long (1957) has attributed many of the conflicting reports of the effect on infection of treatment with cortisone to variations in the susceptibility of different species of animal. The guinea pig, monkey, and man maintained body weight, ,y-globulin synthesis, and antibody production under prolonged treatment with cortisone acetate, whereas rabbits, rats, and mice showed opposite effects, together with an increased susceptibility to infection. The susceptible species often succumb to infection from relatively avirulent organisms such as Actinomyces muris (Long, 1957) or even from saprophytes (Berlin et al., 1952). Mouse macrophages in cell culture differentiate between virulent and avirulent strains of Salmonella typhimurium, a natural pathogen for the mouse. Avirulent organisms do not multiply after phagocytosis. In contrast, the macrophages kill many of the virulent organisms but the survivors multiply and eventually lyse the cells. The ability of an organism to multiply within mononuclear cells is therefore associated with virulence (Furness, 1958a, b). Cortisone may increase the susceptibility of rats and mice to infection, either by inhibiting the production of phagoeytic cells, or by abolishing (or reducing) the bactericidal power of the mature cells, or by a combination of both effects. The cell culture technique of Furness (1958b) has been used to study the effect of cortisone, administered at a level which divides laboratory animals into cortisone-resistant and susceptible species, on the phagoeytic and bactericidal power of macrophages. The results are given in this paper.