A role for activated macrophages in resistance to infection with Toxoplasma.

Activated macrophages from mice which were chronically infected with Toxoplasma gondii or Besnoitia jellisoni, or which had received Freund complete adjuvant, had an enhanced capacity to to kill intracellular Toxoplasma. Enhanced killing by activated macrophages was demonstrated by decreased incorporation of isotopically labeled uridine by intracellular Toxoplasma and by inhibition of plaque formation. The latter resulted from lack of proliferation of the intracellular Toxoplasma which is normally followed by destruction of the host cell (macrophage) and secondary invasion and destruction of fibroblast monolayers.