The first attempt to add a 4-1BB domain (AA214-255) to the PD1/28 receptor by Ankri et al failed due to minimal surface expression of the PD1/28/BB construct,26 but by inserting flexible G4S linkers between functional units, Tang et al generated a functional PD1:CD28:4-1BB receptor, which contains PD1 (AA1-167), CD28 (AA141-220) and 4-1BB (AA214-255).29 Without concurrent expression of a tumor-reactive CAR or TCR, the PD1:CD28:4-1BB receptor alone could efficiently direct human T cells to kill PD-L1-expressing tumor cells and control tumor growth in vivo in humanized mice. Here, CD28 is linked to neoplasm.