indoleamine 2,3-dioxygenase is dispensable for the immunomodulatory function of stem cells from human exfoliated deciduous teeth

objective: in this study, we sought to better understand the immunoregulatory function of stem cells derived from human exfoliated deciduous teeth (shed). we studied the role of the interferon gamma (ifn-γ)-indoleamine 2,3-dioxygenase (ido)-axis in immunoregulation of shed compared to bone marrow derived mesenchymal stem cells (bmmscs) under the same conditions. materials and methods: in this cross-sectional study, recently isolated human t cells were stimulated either by mitogen or inactivated allogeneic peripheral blood mononuclear cells (pbmcs). these t cells were subsequently co-cultured with, either shed or bmmscs in the presence or absence of 1-methyl-tryptophan (1-mt) or neutralizing antihuman- ifn-γ antibodies. in all co-cultures we evaluated lymphocyte activation as well as ido activity. results: shed, similar to conventional bmmscs, had anti-proliferative effects on stimulated t cells and reduced their cytokine production. this property of shed and bmmscs was changed by ifn-γ neutralization. we detected ido in the immunosuppressive supernatant of all co-cultures. removal of ido decreased the immunosuppression of bmmscs. conclusion: shed, like bmmscs, produced the ido enzyme. although ifn-γ is one of inducer of ido production in shed, these cells were not affected by ifn-γ in the same manner as bmmscs. unlike bmmscs, the ido enzyme did not contribute to their immunosuppression and might have other cell-type specific roles.