Moreover, it has been shown that HLA-G can drive macrophage polarization toward a protumoral phenotype, characterized by increased expression IDO, IL-6, and CXCL1, which could result in the inhibition of T cell response and the tumor progression; that is, HLA-G-polarized macrophages act as tumor-associated macrophages at tumor sites (36, 37). Here, IDO1 is linked to neoplasm.