This approach has tremendous potential and may be amenable to in vivo TME modulation by CAR T-cells, particularly in solid tumors where IL-4 is a major contributor towards immunosuppression and neutralization of IL-4 using monoclonal antibodies or deletion of IL-4-expressing T follicular helper cells has been shown to improve T-cell trafficking to tumors and T-cell-mediated anti-tumor functions (112–115). This evidence concerns the gene IL4 and neoplasm.