CD8A and neoplasm: Activated CD4+ and CD8+ T cells are suppressed through engagement of the PD-1 receptor with its ligand PD-L1.71–73 PD-1 is also found on B cells, NK cells, and macrophages, and as such, constitutive PD-L1 expression on GBM tumor cells can induce widespread immunosuppression and alter the tumor microenvironment.