PDCD1 and colorectal carcinoma: There was no difference in their expression levels in PBMC from HDs (2.9 ± 0.5%) and CRC patients (3.7 ± 0.8%), but there was a significant infiltration of CD4+ T cells co-expressing PD-1 and CD39 in TT (40.5 ± 4.5%) compared with NT (13.6 ± 4.5%) and peripheral blood (Figures 2D,E).