CTLA4 and acute myeloid leukemia: The relatively high expression of immune markers such as CD25 and CD69 and increased levels of the regulatory molecules cytotoxic T lymphocyte‐associated protein 4 (CTLA‐4), PD‐1, and PD‐L1, as well as lower levels of HLA‐DR, Fas, and CD62L, suggest that the immune system of AML patients is in a comparative state of initiation or activation.[139, 140, 141] Relevant studies have confirmed the presence of immune imbalance and escape in both AML and MDS patients.