CTLA4 and acute myeloid leukemia: AML cells have also been shown to induce exhaustion in activated T cells via modulating the expression of immune-checkpoint receptors, such as programmed cell death protein-1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) and lymphocyte-activation gene 3 (LAG3).