CD4 and neoplasm: Interestingly, tumor eradication induced by only two infusions of ERBB2-CAR CIK cells enabled survival of the ERBB2-CAR CIK cells, but also led to the expansion and persistence of immune cell subpopulations, namely CD3+CD4+ helper T cells, CD3−CD56+ NK cells, and CD3+CD56+ T-NK cells, which had only been found in very low numbers within the adoptively transferred heterogeneous CIK cell population at the time of infusion (Figures 4A,B, Supplementary Figures 1E,F).