CTLA4 and neoplasm: Persistent exposure of CD8+ T cells to tumour neoantigens can induce the sustained expression of immune-checkpoint molecules, which characterises—and might drive—the dysfunctional state called T-cell exhaustion, in which simple removal of the antigen does not induce recovery.25 Exposure of CD8+ cells to antigens for only a few weeks led to an increased and sustained expression of cytotoxic T-lymphocyte-associated protein (CTLA-4) and subsequently to the development of inactive (exhausted) and apoptotic CD8+ T cells.25