Akin to chronic viral infection and cancer systems, pop3 (KLRG1-CD62Lhi) exhibits the characteristics of stem-like progenitor CD8 T cells (high Tcf7, Slamf6, and Cxcr5 expression), whereas pop4 (KLRG1+CD62Lhi) closely resembles a transitory subset (elevated Tbx21, low Tcf1, and Tox expression). The gene discussed is TOX; the disease is cancer.