IDO1 and neoplasm: Common anti-immune mechanisms uncovered in this study include: 1) downregulation of B-cell stimulation factors (TACI, BCMA, CD27) that likely results in significant depletion of plasma cells, 2) upregulation of chemoattractants of potent immunosuppressive cells (MIF, CXCL1, CXCL2 and CXCR2), 3) upregulation of enzymes (IDO1, TDO2, ARG2) that drain microenvironment from arginine and tryptophan which profoundly inhibit T cell proliferation, 4) defective antigen processing and presentation, which make the proper recognition of tumor cells impossible.