We envisage that the CD25+ T cell subset, containing the CD4+ effector Tregs, could be depleted prior to CAR T cell engineering without any significant risk for harmful autoimmunity as previously shown in humans (95, 96) and that the addition of IL-7 and IL-15 thereafter could optimize the ex vivo expansion of pediatric CAR T cells (69). Here, IL7 is linked to Autoimmunity.