PDCD1 and neoplasm: Our primary analysis centred on the surface expression of 10 immune checkpoints (CD25, CD28, CD39, 4-1BB, CTLA-4, ICOS, OX40, PD-1, PD-L1, and TIGIT) on CD8 + , CD4 + FoxP3-, and CD4 + FoxP3 + T-cell subsets in 35 tumor specimens.