The effects of levamisole on some functions of mouse macrophages after in vitro and in vivo administration.

In vitro incubation of peritoneal macrophages from normal, peptone-stimulated mice with levamisole (1-100 microM) for 1 and 22 h had no effect on either phagocytosis of particulate material (sheep erythrocytes, zymosan) or cellular levels and release of lysosomal enzymes (beta-D-glucuronidase, cathepsin D). By contrast, levamisole 1 and 5 mM dramatically increased enzyme release while inhibiting phagocytosis. In some experiments, however, these high concentrations of levamisole caused an elevated cell mortality. When incubation was extended to 72 h, a decrease of both phagocytosis and enzyme release was observed. The catabolism of endocytosed antigens (sheep erythrocytes, human gammaglobulin) was not at all or only slightly modified depending upon the antigen. The cellular level of cyclic AMP remained unchanged in all experiments. In vivo exposure of macrophages to levamisole (2.5 and 10 mg/kg/day i.p. for 3 days) produced a dose-dependent increase in processing of endocytosed antigens as shown by an enhanced transfer of initially endocytosed material to the macrophage plasma membrane. The other parameters were not modified. The immunogenicity of erythrocytes, when endocytosed by levamisole-treated macrophages and transferred into unsensitized recipients, was increased in some in vivo experiments.