CTLA4 and neoplasm: The inhibitory receptors expressed on T cells, interacting with their corresponding ligands expressed on antigen-presenting cells or tumor cells, such as PD-1/PD-L1, CTLA-4/CD86, TIM-3/Galectin-9, TIGIT/CD155, and BTLA/HVEM, play important roles in regulating T cell functions [15].