FIG. 3.

CD8⁺ T cells mediate protective immunity. A/J mice were vaccinated with 10⁶ tachyzoites of N. caninum. Postvaccination, their splenocytes were isolated and separated with magnetic beads into a purified CD8⁺ population. Approximately 10⁷ splenocytes were transferred directly into naive recipient mice via tail vein inoculation. Control mice received an equivalent number of spleen cells from saline-treated mice. Twenty-four hours after transfer the mice were challenged with 10⁴ PLK strain tachyzoites. Results are representative of two experiments (n = 12 mice/group).