PDCD1 and neoplasm: Interestingly, by stratifying the immune checkpoint molecules, PD-1 and CTLA-4, on T cells by MSI/MSS status, we found fractions of PD-1+ Tcyt cells (Figure 3a) and also PD-1+ Th cells (Supplementary Figure S1a) in some MSS tumours comparable to those in MSI tumours, suggesting there is a similar immune suppression in selected MSS tumours.