FIG. 1.

IFN-γ-deficient mice succumb to acute infection with N. caninum tachyzoites. BALB/c (○ and ▵) and IFN-γ-deficient (⋄ and □) mice were infected i.p. with 2.5 × 10³ N. caninum tachyzoites. ▵ and □, mice treated i.p. with 500 U of recombinant IFN-γ twice a day; ○ and ⋄, untreated mice. The survival of the infected mice was monitored daily, and cumulative mortality was calculated. In the experiment shown, five mice per group were used. Comparable results were obtained in six repeat experiments. (The survival rates of both groups of BALB/c remained at 100% throughout the experiment, and hence triangles overlap with circles.)