The role of macrophages in acquired cell-mediated immunity to Toxoplasma gondii.

Mice immunized by primary infection with an avirulent strain of Toxoplasma gondii were protected against challenge infection with a highly virulent strain, even though macrophages were eliminated either by dextran sulfate or by carbon ink. This findings differs strikingly from previous results obtained in similar experiments with other intracellular pathogens such as Listeria monocytogenes and Salmonella typhimurium. It is therefore concluded that the macrophage population, which plays an essential role in the cell-mediated immunity to reinfection with L. monocytogenes and S. typhimurium, is not of primary importance in cell-mediated immunity to reinfection with T. gondii.