PDCD1 and cancer: CD3D and CD8A were chosen to represent cytotoxic T cells, MSA4 (CD20 surface antigen) and CD19 to represent B cells, CD38 and SLAMF7 (CD319 surface antigen) to represent plasma cells (SDC1, coding for syndecan 1/CD138 surface antigen, was not used because it is also expressed by the SCC tumor epithelia), CD3, CD4, FOXP3 and IL2RA (CD25 surface antigen) to represent regulatory T-cells, and PDCD1 (PD-1) and CD274 (PD-L1) as targets of cancer immune checkpoint blockers.