Fig. 1.

Structural features of T cell receptor versus CAR T cell design. a Structural features of T cell receptor. b Production of CAR T cells from patient-derived T cells. c Structural features of CAR T cell design of different generations. The principal CAR structure includes an extracellular/binding domain, a transmembrane domain, and an intracellular/signaling domain. The extracellular portion of CAR is typically generated from a monoclonal antibody against the target, which is also known as a single-chain variable fragment (ScFv). The ScFv is affixed to the transmembrane domain that crosses the cell membrane via the hinge/spacer region. Following the recognition and binding of ScFv part of the CAR with tumor antigen, the intracellular/signaling domain comprised of co-stimulators and the CD3ζ chain initiates intracellular signaling. The first-generation CAR contains only immunoreceptor tyrosine-based activation motif (ITAM) motifs in the intracellular domain. The second-generation CAR includes one co-stimulatory molecule, and the third-generation CAR contains two co-stimulatory molecules. The fourth and fifth generations of CARs are based on second-generation CAR. The fourth-generation CAR contains 1–3 immunoreceptor tyrosine-based activation motifs combined with an inducible expressed cytokine; while the fifth-generation CAR is T cell receptor-deficient CAR T cells developed employing genome editing technologies