Infection of murine peritoneal macrophages with Toxoplasma gondii exposed to ultraviolet light.

Exposure of Toxoplasma trophozoites to ultraviolet light (UV; 2,539 A) remarkably inhibited intracellular multiplication of the toxoplasmas within cultured mouse peritoneal macrophages. These toxoplasmas possessed the ability to induce normal parasitophorous vacuoles (PV) and underwent gradual degeneration in the PV without participation of host-cell lysosomes. Apparently, the basic conformation of the PV, i.e., the association of mitochondria, rough endoplasmic reticulum, and microtubules of the host cell and the presence of microvillous infoldings, was maintained as seen under the electron microscope even after the toxoplasmas had died within the PV. Even PV, in which debris of the toxoplasmas could be observed, did not show the sign of fusion with ferritin-labeled secondary lysosomes.