In summary, here, we delineate upregulation of p40 in breast cancer patients, human TNBC cells and PDX mouse model of TNBC and demonstrate that scavenging of p40 by p40 mAb enriches anti-oncogenic CD4+IFNγ+ and CD8+IFNγ+ T cells, enriches M1 macrophages, downregulates M2 macrophages, suppresses TGFβ signaling, and induces apoptosis and/or necrosis, leading to tumor regression in a PDX mouse model of TNBC. The gene discussed is CD8A; the disease is breast cancer.