The basic CAR structure consists of an extracellular antigen-recognition domain attached to an extracellular spacer domain, a trans-membrane region that anchors the receptor in the plasma, and a signaling endodomain. The single-chain antibody fragment (scFv) consisting of a variable heavy (VH) and a variable light (VL) chain, both of which are derived from the same parental antibody and linked by a flexible linker.