biostudies-literatureWen ZNatural Science Foundation of Zhejiang ProvinceNational Natural Science Foundation of ChinaNatural Science Foundation of Zhejiang Province (Zhejiang Provincial Natural Science Foundation)National Natural Science Foundation of China (National Science Foundation of China)2362https://www.ebi.ac.uk/biostudies/studies/S-EPMC11893787biostudies-literatureUnknown16(1)Overcoming immunosuppression in the tumor microenvironment (TME) is crucial for developing novel cancer immunotherapies. Here, we report that IL-16 administration enhances the polarization of T helper 1 (Th1) cells by inhibiting glutamine catabolism through the downregulation of glutaminase in CD4⁺ T cells and increases the production of Th1 effector cytokine IFN-γ, thus improving anti-tumor immune responses. Moreover, we find that establishing an IL-16-dependent, Th1-dominant TME relies on mast cell-produced histamine and results in the increased expression of the CXCR3 ligands in tumor-associated macrophages (TAM), thereby improving the therapeutic effectiveness of immune checkpoint blockade (ICB). Cancer patients exhibit impaired production of IL-16, which correlates with pooNature communicationsInterleukin-16 enhances anti-tumor immune responses by establishing a Th1 cell-macrophage crosstalk through reprogramming glutamine metabolism in mice.PMC11893787LY22H16000381970484821717308227287281930041U22A20307Shen MWen ZLu YLiu TAcharya NHou YZhao YWang KShen ZGuo KWang PDing YShang MGuo HChen WShen SCui BLi HPan TXu JXiao PLi SHuang YQingqing WXu XCao QfalseInterleukin-16 enhances anti-tumor immune responses by establishing a Th1 cell-macrophage crosstalk through reprogramming glutamine metabolism in mice.Overcoming immunosuppression in the tumor microenvironment (TME) is crucial for developing novel cancer immunotherapies. Here, we report that IL-16 administration enhances the polarization of T helper 1 (Th1) cells by inhibiting glutamine catabolism through the downregulation of glutaminase in CD4⁺ T cells and increases the production of Th1 effector cytokine IFN-γ, thus improving anti-tumor immune responses. Moreover, we find that establishing an IL-16-dependent, Th1-dominant TME relies on mast cell-produced histamine and results in the increased expression of the CXCR3 ligands in tumor-associated macrophages (TAM), thereby improving the therapeutic effectiveness of immune checkpoint blockade (ICB). Cancer patients exhibit impaired production of IL-16, which correlates with poo2025-01-01T00:00:00Z2025 Mar2026-06-01T18:01:30.746Z2025-04-04T00:21:30.73ZS-EPMC118937874006491810.1038/s41467-025-57603-1