CD4 and neoplasm: The findings of ACT in clinical trials and animal studies suggest that the differentiation state of the adoptively transferred cells, the use of lymphodepletion and strategies to boost T-cell proliferation after adoptive transfer influence the efficacy of ACT.9, 10, 11, 12 Previously, we have shown that CD4+ T helper 1 (Th1) cells were able to enhance CD8+ CTL-mediated tumour rejection without systemic administration of recombinant IL-2.13 The differentiation state is an important determinant for the longevity of the adoptively transferred T cells.