Some key points during the process of manufacturing CAR T cells. a The progress of T cells with the associated characteristics. As TN cells differentiate, the proliferative capacity of T cells is gradually reduced. Except for TE cells, the remaining subsets have a self-renewal ability, which declines from TN to TEM cells. Therefore, it is best to choose TSCM cells for CAR T cell generation. b Adding IL-7/IL-15 during in vitro expansion has a positive impact. IL-7/IL-15 can increase the proportion of TSCM cells and contribute to maintaining the ratio of CD4+:CD8+ cells.