Strong cytolytic activity of natural killer cells is neither necessary nor sufficient for preimmune resistance to Toxoplasma gondii infection.

: That strong cytolytic activity of natural killer (NK) cells is neither necessary nor sufficient for defense against acute Toxoplasma gondii infection is demonstrated. T. gondii-infected anti-interferon (IFN)-gamma-treated mice and IFN-gamma gene knockout mice died despite good induction of NK activity, while infected beige mice, deficient in NK cytolytic activity, survived.