TNF and neoplasm: Tumor models have shown that N2-TAN-mediated immune suppression was achieved through various mechanisms: 1) production of TNF-α and NO to induce T cell apoptosis (132); 2) inhibition of T cell proliferation through modulation of PD-1/PD-L1 signaling and release of arginase (133); 3) N2-TAN expression of TGF-β, and 4) production of CCL17, shown to recruit Tregs to further induce an immunosuppressive state (134).