It would also be possible that the process of activating anti-cyst CD8+ cytotoxic T cells and/or initiating the anti-cyst process by the CD8+ cytotoxic T cells are more vulnerable to the negative environment induced by the susceptible genetic background of C57BL/6 mice to the infection than the process of activating IFN-γ-producing CD8+ T cells against tachyzoites and operating IFN-γ-mediated prevention of tachyzoite growth. This evidence concerns the gene CD8A and cyst.