Abstract
Significantly larger numbers of Toxoplasma gondii cysts were detected in the brains of RAG1(-/-)NOS2(-/-) than RAG1(-/-) mice following infection. In contrast, the cyst numbers markedly decreased in a same manner in both strains of mice after receiving CD8(+) immune T cells. Thus, NOS2-mediated innate immunity is important for inhibiting formation of cysts in the brain but not required for the T cell-initiated cyst removal, which is associated with phagocyte accumulation. Treatment with chloroquine, an inhibitor of endolysosomal acidification, partially but significantly inhibited the T cell-mediated cyst removal, suggesting that phagosome-lysosome fusion could be involved in the T. gondii cyst elimination.