In CrT-KO mice, tumor-infiltrating CD8 T cells expressed higher levels of PD-1, which has been associated with bioenergy insufficiency and T cell exhaustion, indicating that CrT deficiency may impact antitumor T cell activities (Fig. 1, E–G; Chang et al., 2015; Wherry and Kurachi, 2015; Bengsch et al., 2016). The gene discussed is SLC6A8; the disease is neoplasm.