Many cytokines and transcription factors contribute to the development of T cell heterogeneity, and during toxoplasmosis these include the cytokines IL-7 and IL-12 [11,73], as well as transcription factors T-bet, c-Rel, BLIMP1, STAT1, and Bhlhe40 [74–79], yet it is unclear whether secondary antigen encounter and TCR activation alters CD8+ T cell fate decisions. This evidence concerns the gene PRDM1 and toxoplasmosis.