They co-cultured these cells with CD123 and PD-L1 positive acute myeloid leukemia (AML) cell lines and found that the CAR-T cells with the CD28 costimulatory domain showed diminished proliferative capacity and cytokine production as compared to the other CAR constructs, indicating that CD28 CAR-T cells might be more prone to exhaustion than their 4.1BB counterpart [83]. Here, CD28 is linked to acute myeloid leukemia.