CD39 expression among T cells can signify several populations, including CD39+CD103−CD4+ T cells associated with transcriptomic signatures of a highly suppressive regulatory phenotype predictive of poor outcome and exhausted yet highly cytotoxic CD39+CD103+ CD8+ T cells which are able to infiltrate the tumor nest where their presence is linked to improved overall and RFS at 5 years in a cohort of early treatment naïve NSCLC patients. The gene discussed is CD8A; the disease is non-small cell lung carcinoma.