Previous studies have demonstrated that whole leukemia cell vaccines are suppressed by various immunosuppressive mechanisms of leukemia, including B7/cytotoxic T lymphocyte-associated protein 4 (CTLA4) and PD-1/PD-L1, Tregs, and myeloid-derived suppressor cells (MDSCs) [42, 148]. Here, CTLA4 is linked to leukemia.