PDCD1 and neoplasm: Furthermore, a significant correlation was observed between the percentages of CD3 + PD-1+, CD3+ CD4+ PD-1+ or CD3+ CD4+ CD25+ FOXP3+ PD-1+ lymphocytes in PBMCs and the level of PD-L1 expression detected by IHC in tumor tissue (p < 0.05, Fig. 5d).