Among these ten groups, two or three might be of particular interest in the context of cancer biology [30]: the regulatory T cell phenotype driven by FOXP3 and partially FOXO1 (referred to as Treg in the model), and Th1 (CD4+) or cytotoxic (mostly CD8+ but also CD4+) phenotypes driven by Tbet (T-box transcription factor TBX21) (referred to as Th1_CTL in the model). The gene discussed is CD8A; the disease is cancer.