Original Article

Immunology and Cell Biology (2016) 94, 747–762; doi:10.1038/icb.2016.34; published online 10 May 2016

Human macrophages induce CD4+Foxp3+ regulatory T cells via binding and re-release of TGF-β

Angelika Schmidt1, Xing-Mei Zhang2, Rubin N Joshi1, Shasina Iqbal1,4, Casper Wahlund3, Susanne Gabrielsson3, Robert A Harris2,5 and Jesper Tegnér1,5

  1. 1Unit of Computational Medicine, Center for Molecular Medicine, Department of Medicine Solna, Karolinska Institutet, Karolinska University Hospital, & Science for Life Laboratory, Stockholm, Sweden
  2. 2Applied Immunology & Immunotherapy, Center for Molecular Medicine, Karolinska University Hospital at Solna, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
  3. 3Translational Immunology Unit, Department of Medicine Solna, Karolinska Institutet & Karolinska University Hospital, Stockholm, Sweden

Correspondence: Dr A Schmidt, Unit of Computational Medicine, Center for Molecular Medicine, Department of Medicine Solna, Karolinska Institutet, Karolinska University Hospital L8:05, S-17176 Stockholm, Sweden. E-mail: angelika.schmidt@ki.se; Professor RA Harris, Applied Immunology & Immunotherapy, Department of Clinical Neuroscience, Karolinska Institutet, CMM L8:04, Karolinska Hospital, S-17176 Stockholm, Sweden. E-mail: Robert.Harris@ki.se

4Current address: EUFETS GmbH, Idar-Oberstein, Germany.

5Shared senior authorship.

Received 12 September 2015; Revised 8 April 2016; Accepted 9 April 2016
Advance online publication 10 May 2016

Top

Abstract

While pro-inflammatory immune responses are a requirement to combat microbes, uncontrolled self-directed inflammatory immune responses are the hallmark of autoimmune diseases. Restoration of immunological tolerance involves both suppression of ongoing tissue-destructive immune responses and re-education of the host immune system. Both functionally immunosuppressive macrophages (M2) and regulatory T cells (Tregs) are implicated in these processes. Their mutual interaction is synergistic in this context and adoptive transfer of each cell type has been functioning as immunotherapy in experimental models, being particularly effective when using M2 macrophages generated with an optimized interleukin-4 (IL-4)/interleukin-10 (IL-10)/transforming growth factor-β (TGF-β) combination. As a prerequisite for eventual translation of M2 therapy into clinical settings we herein studied the induction, stability and mechanism of generation of human induced Tregs (iTregs) by M2 macrophages generated with IL-4/IL-10/TGF-β. The supernatants of monocyte-derived human M2 macrophages robustly induced FOXP3 and other Treg signature molecules such as CTLA-4 and IKZF4 in human naïve CD4 T cells. M2-induced iTregs displayed enhanced FOXP3 stability and low expression of pro-inflammatory cytokines interferon-γ and IL-17, as well as functional immunosuppressive activity compared with control T cells. The FOXP3-inducing activity was dependent on TGF-β, which was both expressed and captured with re-release by M2 macrophages into the soluble supernatant fraction, in which the TGF-β was not confined to extracellular vesicles such as exosomes. We propose that adoptive transfer of human M2 macrophages may be exploited in the future to induce Tregs in situ by delivering TGF-β, which could be developed as a therapeutic strategy to target autoimmune and other inflammatory diseases.