Pioneering work in the murine lymphocytic choriomeningitis virus (LCMV) model has mapped the molecular and phenotypic profiles of CD8+ T cells with acute resolving and chronic infections3–5, revealing progenitors of exhausted T cells, defined by the expression of transcription factors, TOX and TCF1, which arise in the acute-phase of infection and sustain terminally exhausted subsets over the long-term6–9. The gene discussed is TCF7; the disease is infection.