FIG. 6.

Both β₂-microglobulin and Aβ KO mice, which lack MHC class I-restricted CD8⁺ and class II-restricted CD4⁺ T lymphocytes, respectively, are susceptible to normally nonlethal T. gondii infection. Animals were infected by intraperitoneal injection of 20 cysts of the low-virulence ME49 parasite strain, and survival was monitored. Strain C57BL/6 mice (wild-type counterparts to the KO strains) do not begin to succumb to infection until approximately 100 days postinfection (48).