HLA-G and neoplasm: For instance, KYNU-derived 3-hydroxyanthranilate (3-HAA) has been shown to inhibit NO production in macrophages, preventing macrophage-mediated tumor killing [31], induce HLA-G cell surface expression in dendritic cells, enhancing dendritic cells’ ability to tolerate antigens [32], induce apoptosis in both cytotoxic T-cells and Th1 populations of effector T cells [33,34], and enhance differentiation of Tregs [35,36].