Mycobacterium bovis BCG: Characterization of the Experimental System

The macrophage migration inhibition test was applied to the study of delayed hypersensitivity in mice vaccinated intravenously with oil-treated cell walls of Mycobacterium bovis BCG. Migration inhibition of peritoneal exudate cells from sensitized mice was demonstrated directly upon incubation of the cells with purified protein derivative, but indicator cells such as normal peritoneal cells had to be included to demonstrate migration and migration inhibition with sensitized lung cells. Inhibition of migration induced by mouse cells was greatest 3 to 4 weeks after sensitization but was still considerable after 11 weeks. The migration inhibitory factor (MIF) was not detected in cells freshly isolated from sensitized mice but was released into the supernatant fluid when cells were incubated with purified protein derivative for 24 hr at 37 C in a tissue culture system. Production of MIF was inhibited by actinomycin D and puromycin. MIF was nondialyzable, resistant to heating at 56 C for 1 hr, and of a lower molecular weight than mouse gamma globulin. All data indicated that migration inhibition induced by cells from cell wallvaccinated mice was very similar to that caused by guinea pig lymphocytes.