IDO1 and lobular neoplasia: In conclusion, this study for the first time discovered that IL-27 could increase the production of Kyn and Kyna in MSCS by activating the JAK1–STAT1 signaling pathway, promote MSC transformation into anti-inflammatory MSC2, increase the population of IDO+ stem cells, and enhance MSC immune regulation function (Fig. 9); Kyna increased the production of the anti-inflammatory factor TSG-6 by binding with AHR and improved the effectiveness of MSCS in LN mice.