CTLA4 and neoplasm: Many immune checkpoints are initiated by ligand-receptor interactions, and the receptors involved in such interactions include cytotoxic T lymphocyte-associated protein-4 (CTLA4), the PD1 receptor expressed in activated T cells, and the PDL1 and PDL2 receptors expressed on immune and tumor cells (Pardoll, 2012; Batlevi et al., 2016).