In addition, enhanced TAM polarization toward the M2 phenotype with immunosuppressive features assists tumor evasion from immune surveillance and limits the activity of infused redirected CAR T cells in tumor sites through multiple pathways, including the release of immunosuppressive mediators (such as IL-10, TGF-β, and IDO), the expression of immune checkpoint molecules, and recruiting regulatory T cells [102, 103]. Here, IDO1 is linked to neoplasm.