PDCD1 and neoplasm: When we examined the TILs from early (6 mos), intermediate (8 mos) and late (12 mos) stage post-DEN tumours from these mice by flow cytometry, we found significantly higher proportions of Foxp3+CD25+CD4+ Treg and PD-1+ exhausted CD8+ T cells, alongside significantly lower proportions of CD69+ active CD8+ T cells and NK 1.1+ NK cells at intermediate stage tumours at 8 mos post DEN induction (Fig. 6c, d and Supplementary Fig. 8a).