title: mTOR Inhibition Per Se Induces Nuclear Localization of FOXP3 and Conversion of Invariant NKT (iNKT) Cells into Immunosuppressive Regulatory iNKT Cells.
abstract: CD1d-restricted activation of invariant NKT (iNKT) cells results in the abundant production of various types of cytokines and the subsequent modulation of immune responses. This has been shown to be relevant in several clinical disorders, including cancer, autoimmunity, and graft tolerance. Although it is well known that the suppressive function of regulatory T cells is critically dependent on the FOXP3 gene, FOXP3 can also be expressed by conventional human T cells upon activation, indicating the lack of specificity of FOXP3 as a marker for suppressive cells. In this study, we report that the mammalian target of rapamycin (mTOR) inhibitor rapamycin and IL-10, but not TGF-β, can induce FOXP3 expression in iNKT cell lines. Importantly, however, FOXP3(+) iNKT cells only acquired suppressive abilities when cultured in the presence of the mTOR inhibitor rapamycin. Suppression of responder T cell proliferation by FOXP3(+) iNKT cells was found to be cell contact-dependent and was accompanied by a reduced capacity of iNKT cells to secrete IFN-γ. Notably, imaging flow cytometry analysis demonstrated predominant nuclear localization of FOXP3 in suppressive FOXP3(+) iNKT cells, whereas nonsuppressive FOXP3(+) iNKT cells showed a predominance of cytoplasmically localized FOXP3. In conclusion, whereas IL-10 can enhance FOXP3 expression in iNKT cells, mTOR inhibition is solely required for promoting nuclear localization of FOXP3 and the induction of suppressive FOXP3(+) iNKT cells.
authors.affiliation: Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands; and c.huijts@vumc.nl jj.vandervliet@vumc.nl.
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: Huijts
authors.affiliation: Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands; and.
authors.forename: Famke L
authors.initials: FL
authors.lastname: Schneiders
authors.affiliation: Department of Molecular Cell Biology and Immunology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Garcia-Vallejo
authors.affiliation: Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands; and.
authors.forename: Henk M
authors.initials: HM
authors.lastname: Verheul
authors.affiliation: Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands; and.
authors.forename: Tanja D
authors.initials: TD
authors.lastname: de Gruijl
authors.affiliation: Department of Medical Oncology, VU University Medical Center, 1081 HV Amsterdam, the Netherlands; and c.huijts@vumc.nl jj.vandervliet@vumc.nl.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: van der Vliet
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000276:immunology; D060908:CTLA-4 Antigen / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D051858:Forkhead Transcription Factors / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007166:Immunosuppressive Agents / Q000276:immunology / Q000494:pharmacology; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D016753:Interleukin-10 / Q000276:immunology / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D055611:Natural Killer T-Cells / Q000276:immunology* / Q000378:metabolism; D020123:Sirolimus / Q000276:immunology / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology* / Q000378:metabolism
chemical_list: D060908:CTLA-4 Antigen; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D007166:Immunosuppressive Agents; D016753:Interleukin-10; D007371:Interferon-gamma; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus