Infected cells are sufficient to induce CD4⁺ and CD8⁺ T cell responses.

<p>Bone marrow-derived dendritic cells were cultured overnight with Violet-labeled, mCherry-expressing <i>cpsII</i> parasites. The following day, dendritic cells were sorted into mCherry^+veViolet^+ve (infected) and mCherry^+veViolet^−ve (uninfected) populations and 10⁴ dendritic cells from each population were administered to mice. In parallel, dendritic cells that had phagocytosed <i>T. gondii</i> were obtained by sorting on bone marrow-derived dendritic cells that were incubated with invasion-blocked Violet-labeled, mCherry-expressing <i>cpsII</i> parasites. 10 days later, mice were sacrificed and CD4⁺ (a) and CD8⁺ (b) T cell responses in the peritoneal cavity and spleen were analyzed. Populations shown depicting CD4⁺-tetramer binding are enriched for the tetramer^+ve population and these cells were isolated from the spleen (a, bottom). All other cell populations shown were harvested from the peritoneal cavity, although similar trends were apparent when splenocytes were examined. Flow plots are gated on Foxp3^−ve CD4⁺ T cells (a, top), CD4⁺ T cells (a, bottom) or CD8⁺ T cells (b). Parasite burdens from the PECS of mice transferred infected dendritic cells or dendritic cells that have phagocytosed <i>T. gondii</i> 5 days post-challenge with 10³ tachyzoites of a highly virulent, replicating strain of <i>T. gondii</i>, administered 6 weeks following vaccination with 10⁴ infected or uninfected dendritic cells, analyzed by flow cytometry (c). Significance in (c) was determined using a Mann-Whitney U-test. *p<0.05; **p<0.005. AVG±SE.