CTLA4 and neoplasm: ICIs such as those targeting the CTLA-4 and PD-1 pathways provide a means of overcoming the ability of tumor cells to suppress T cell activity, thereby restoring effective T cell-mediated tumor recognition and killing.358 The binding of PD-L1 to PD-1 triggers co-inhibitor signaling that inhibits the activation and function of effector T cells, instead favoring regulatory T cell differentiation and activity in a manner that suppresses adaptive immunity.