PDCD1 and brain neoplasm: Specifically, programmed death-ligand 1 (PD-L1), programmed cell death receptor 1 (PD-1), lymphocyte activation gene 3 (LAG-3), and T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) have all been implicated in cluster of differentiation (CD)-8+ T-cell exhaustion [10-17], although the precise role of these markers in brain-tumor-mediated immunosuppression is unclear.