Furthermore, immunosuppressive factors in the TME also hinder the effects of CAR-T cells, like tumor-associated macrophages (TAM), regulatory T (Treg) cells, myeloid-derived suppressor cells (MDSCs) and tumor-associated fibroblasts (TAFs) could directly inhibit CAR-T cells, and many cytokines like transforming growth factor beta (TGF-β), IL-4, IL-10 could promote infiltration of suppressive immune cells, thereby indirectly inhibiting CAR-T. The gene discussed is IL4; the disease is neoplasm.