Nevertheless, it has been shown that PD-1loCD8+ TIL removed early after tumor injection (likely containing an increased frequency of TCF-1+ cells) followed by transfer into naïve hosts and infection with Listeria monocytogenes 3-4 weeks later can mount a memory response whereas fully exhausted PD-1hiCD8+ TIL isolated at later time points cannot (18). The gene discussed is TCF7; the disease is infection.