Insights on the mechanisms of the protective immunity in the brain from the studies on infection with an intracellular microorganism, Toxoplasma gondii

The immune system operates the protection against infections by selecting efficient pathways depending on pathogen. Toxoplasma gondii, an obligate intracellular protozoan parasite, has two lifecycle stages, tachyzoite and cyst, in intermediate hosts including humans. Tachyzoite is acute stage form that quickly proliferates within host cells. Cyst chronic can slowly grow into more than 100 mm diameter containing hundreds to thousands of bradyzoites. Our studies IFN-g-mediated protective immunity cerebral growth revealed IFN-g production brain-resident cells not only required for upregulation innate limit proliferation during early but also crucial recruiting T from periphery activation recruited ultimately prevent growth. Since various microorganisms brain, it possible IFN-gproduced plays a key first line defense role orchestrating both cell-mediated control T. gondii other pathogens. cysts uncovered capability cytotoxic penetrate target perforin-dependent manner its elimination. After penetrating target, secrete granzyme B, which associates with accumulation phagocytes eliminate parasite. presence tumor-infiltrating CD8+ solid cancers indicator positive prognosis cancer patients, perforin-mediated penetration could function as powerful mechanism gondiicysts targets large mass general such cancers.