Figure 1.

The development of the five generations of CAR. 1^st:ITAM area containing only CD3. 2^nd:On the basis of the first generation, a co-stimulatory region (CD28 or 4-1BB) was introduced. 3^rd: On the basis of the second generation, two co-stimulatory regions (CD28 and 4-1BB) were introduced. 4^th:Introducing the regulation of CAR-T cell structure, such as cytokines and chemokine receptors. 5^th: Creating allogeneic CAR-T cells by knocking out endogenous T cell receptors (TCRs) and leukocyte antigen class I molecules (HLAs).