Numerous studies have determined that cell surface markers (e.g., CD39) and genes associated with terminal exhaustion (e.g., CXCL13) can efficiently distinguish bystander from tumor-specific CD4 and CD8 T-cells [Hanada et al., 2022, Veatch et al., 2022, Oliveira and Wu, 2023]. The gene discussed is ENTPD1; the disease is neoplasm.