CAR T cells, a type of genetically engineered peripheral T cell, have a special antigen receptor whose extracellular single-chain variable fragment (scFv) can directly recognize a specific antigen independent of the major histocompatibility complex (MHC), an intracellular CD3ζ domain that conveys the T-cell activation signal, and a CD28 or 4-1BB domain that provides a costimulatory signal to facilitate the proliferation of CAR T cells and enable them to persistently attack tumor cells (7). Here, CD28 is linked to neoplasm.