Importantly, the expression of CD39, a marker for exhausted T cells33,34, is only induced in tumor CD8+ T cell, during tumor growth in WT mice (Supplementary Fig. 2f), and even higher levels in tumor CD8+ T cell from NcDase−/− mice (Supplementary Fig. 2f), but not in CD8 T cells from other tissues. The gene discussed is ENTPD1; the disease is neoplasm.