CD4 and neoplasm: Previous research showed that the persistence of CAR‐T cells is in line with their anti‐tumor effect and high CD8 T cell to CD4 T cell ratio results in better therapeutic effect of adoptive cell therapy.23, 24 In the same animal work as shown in Figure 4A, we measured T‐cell number in mouse circulation and the ratio of CD8 T cell to CD4 T cell.