IDO1 scavenges reactive oxygen species in myeloid-derived suppressor cells to prevent graft-versus-host disease

Ji Min Ju, Giri Nam, Young Kwan Lee, Minho Jung, Hanna Chang, Woojin Kim, Woo Jeong Shon, Ji Young Lim, Joo Young Kim, Jun Chang, Chang Ki Min, Dong Sup Lee, Kyungho Choi, Dong Mi Shin, Eun Young Choi

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase 1 (IDO1) also has an immunological function to suppress T cell activation in inflammatory circumstances, including graft-versus-host disease (GVHD), a fatal complication after allogeneic bone marrow transplantation (allo-BMT). Although the mononuclear cell expression of IDO1 has been associated with improved outcomes in GVHD, the underlying mechanisms remain unclear. Herein, we used IDO-deficient (Ido1-/-) BMT to understand why myeloid IDO limits the severity of GVHD. Hosts with Ido1-/- BM exhibited increased lethality, with enhanced proinflammatory and reduced regulatory T cell responses compared with wild type (WT) allo-BMT controls. Despite the comparable expression of the myeloid-derived suppressor cell (MDSC) mediators, arginase-1, inducible nitric oxide synthase, and interleukin 10, Ido1-/- Gr-1+CD11b+ cells from allo-BMT or in vitro BM culture showed compromised immune-suppressive functions and were skewed toward the Ly6ClowLy6Ghi subset, compared with the WT counterparts. Importantly, Ido1-/-Gr-1+CD11b+ cells exhibited elevated levels of reactive oxygen species (ROS) and neutrophil numbers. These characteristics were rescued by human IDO1 with intact heme-binding and catalytic activities and were recapitulated by the treatment of WT cells with the IDO1 inhibitor L1-methyl tryptophan. ROS scavenging by N-acetylcysteine reverted the Ido1-/-Gr-1+CD11b+ composition and function to an MDSC state, as well as improved the survival of GVHD hosts with Ido1-/- BM. In summary, myeloid-derived IDO1 enhances GVHD survival by regulating ROS levels and limiting the ability of Gr-1+CD11b+ MDSCs to differentiate into proinflammatory neutrophils. Our findings provide a mechanistic insight into the immune-regulatory roles of the metabolic enzyme IDO1.

Original languageEnglish
Article numbere2011170118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number10
StatePublished - 9 Mar 2021

Bibliographical note

Publisher Copyright:
© 2021 National Academy of Sciences. All rights reserved.


  • GVHD
  • Gr-1+CD11b+ cell
  • IDO
  • Myeloid-derived suppressor cell
  • ROS


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