Inhibition Of Indoleamine 2,3-dioxygenase Activity Promotes Function Of Dendritic Cells Derived From Chronic Myeloid Leukemia

ObjectiveDendritic cells(DCs) are the most powerful profession antigen-presenting cells(APCs) in vivo and play a crucial central role in the outcome of several immune responses.DCs have been successfully used in clinical trails to induce tumor-specific immunity.Although the DCs derived from leukemia patients have the similar morphology and immunophenotype with DCs from normal individuals,the immunological function are weaker.Indoleamine 2,3-dioxygenase(IDO) is the rate-limiting enzyme in the catabolism of tryptophan along the kynurenine pathway,which is widely distributed in the body.IDO enzymatic activity results in the local depletion of tryptophan and a local increase in the concentration of downstream metabolites.The decrease in tryptophan and the local increase in tryptophan metabolites can cause cell cycle arrest,anergy induction in responding T cells,and differentiation of new Tregs from uncommitted CD4~+T cells.IDO has been confirmed negative regulation of immune and participated in tumor immune escape. Expressions of IDO were obviously higher after DC maturation.To investigate the expression of indoleamine 2,3-dioxygenase(IDO) in dendritic cells derived from chronic myeloid leukemia(CML-DCs) and to study the influence of IDO activity inhibition on the function of CML-DCs.MethodsAfter inspection of Hematology,bone marrow,chromosome and molecular,a clear diagnosis of chronic myeloid leukemia.Bone marrow mononuclear cells(BMMNCs) were isolated from CML patients by density ~gradient centrifugation and were cultured in RPMI-1640 culture medium supplemented with recombinant human(rh) GM-CSF and rhIL-4.The expressions of IDO mRNA in dendritic cells derived from chronic myeloid leukemia were detected by RT-PCR.The phenotypes of CML-DCs were analyzed by flow cytometry.The immature CML-DCs (imDC) and the mature CML-DCs(mDC) were used as stimulating cells and autologous T-lymphocytes were used as reactive cells for a mixed lymphocyte reaction system.IL-12 concentrations were detected by ELISA kits;Mixed lymphocyte reaction were analyzed by MTT assay.ResultsIt was demonstrated that DCs derived from bone marrow mononuclear cells of CML displayed the typical morphology of DCs. Expressions of co-stimulatory molecules on DCs,such as CD80,CD86, CD83 and HLA-DR,except for CDla,were obviously higher after maturation(P＜0.05) and were not be influenced by 1-methyltryp tophan (1-MT).Inhibition IDO activity in mature and immature DCs by 1-MT significantly enhanced their abilities to activated T cells proliferation and to produce IL-12(P＜0.05,P＜0.01).ConclusionThis study indicates that the expression of IDO mRNA on DCs derived from CML could be upregulated in the presence of GM-CSF, IL-4 and TNF-a.Inhibition IDO activity in CML-DC can increases their abilities to produce IL-12 and activate autologous T cells.Negative regulation of DCs by IDO paves a way for DC-based leukimia immuntherapy.