Figure 1.

Schematic representation of CAR structure. CAR T cells are composed of three parts: (1) an scFv, (2) a transmembrane domain, and (3) a signal transduction domain of the TCR. First-generation CARs used a CD3ζ as the signal transduction domain of the TCR, whereas second-generation CARs include additional co-stimulatory signaling domains (CD28 or 4-1BB). Third-generation CARs consist of two distinct co-stimulatory domains, such as both CD28 and 4-1BB. Fourth-generation CARs are additionally armored with genes that enable, for example, the expression of cytokines.

CAR, chimeric antigen receptor; scFv, single-chain variable domain of an antibody; TCR, T-cell receptor.