PDCD1 and neoplasm: Although all constructs were able to ameliorate CAR T cell effector function and proliferation in response to PD-L1+ tumour cells and showcase the potential of IFPs as a novel approach for interrupting the PD-1-PD-L1 axis, only PTM, CTM, and CTMΔ12EC IFPs complement the CAR without the adverse potential of inducing a CAR-independent T cell response.