CTLA4 and neoplasm: Recently, there has been active research into vaccine combinations involving checkpoint inhibitors, such as anti-CTLA-4 or anti-PD-1/PD-L1, to enable the vaccine-induced T cells to enter the tumor and function there without being inhibited by ligands like PD-L1 (Gatti-Mays et al., 2017; Parch et al., 2016).