IDO1 and myeloid sarcoma: These results were followed by the failure of another group to detect a significant baseline difference in the plasma l-kynurenine/Trp ratio between relapsing-remitting MS and control samples; however, an increased l-kynurenine/Trp ratio was detected after treatment with INF-β, implicating IDO activation as a potential mode of action of INF-β products widely used in the first-line treatment of MS and clinically isolated syndrome (CIS) [202].