CTLA4 and neoplasm: Chronic exposure to tumor-associated antigens and expression of PD-L1 by tumor cells also impairs T-cell function, and tumor-infiltrating lymphocytes from HCC samples have been shown to be poorly functional and exhausted, expressing high levels of PD-1, TIM-3, LAG-3, or CTLA-4, and consequently failing to control tumor development.10, 11