CD28 and acute myeloid leukemia: Mardiros et al. reported the development of second-generation CD123 CAR-T cells using a vector containing a single-chain variable fragment, a IgG4 linker, a CD28 co-stimulatory domain, and a CD3 zeta domain used to engineer either autologous or donor-derived T lymphocytes; these cells exhibited potent effector activity against primary AML cells and exerted only a limited cytotoxicity in vitro against hematopoietic progenitor cells [107].