CD8A and neoplasm: It is important to note that the expression of PD-1, CTLA-4, LAG-3, TIM-3, and TIGIT receptors does not occur only at the level of tumor-specific T cells, namely CD8+ cytotoxic T cells and CD4+ Th1 cells, but also in other cells involved in anti-tumor immunity, such as NK cells, consequently impairing functions that are involved in the recognition of malignant cells and subsequently in anti-tumor cytotoxicity with the secretion of cytokines.