Figure 1.

Evolution of CAR design. First-generation CARs mediate antigen recognition and T-cell activation through the fusion of an extracellular ­antigen-binding single-chain variable region (scFv) with an intracellular signaling domain from the CD3ζ chain. In this way, surface antigens can be recognized by CAR T cells independent of major histocompatibility complex (MHC)–mediated presentation. Second-generation CARs provide combined activation and costimulatory signals through the addition of the intracellular domain of costimulatory receptors. Third-generation CARs consist of two costimulatory domains. In the latest fourth-generation design, CARs are coexpressed with enzymes, cytokines, and costimulatory ligands or receptors transferred with the same vector construct. TM, transmembrane.