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

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.

Immunomodulation By Therapeutic Mesenchymal Stromal Cells (MSC) Is Triggered Through Phagocytosis of MSC By Monocytic Cells

“…Multiple studies have reported increased frequencies of Tregs cells in experimental animal studies and in patients treated with MSC . It has furthermore been shown that immunosuppressive macrophages (M2) can induce Tregs cells in vitro . Our results give insight in how MSC driven polarization of monocytic cells may mediate increasing Tregs cell numbers after MSC infusion.…”

Prediction of steroid demand in the treatment of patients with ulcerative colitis by immunohistochemical analysis of the mucosal microenvironment and immune checkpoint: role of macrophages and regulatory markers in disease severity

“…Therefore, the immunosuppressive function of CD163 + macrophages might be mediated by PD‐L1/L2. Importantly, human macrophages induce FOXP3 + Tregs via binding and rerelease of TGFB, the checkpoint inhibition . Although not statistically significant, a trend of association with SR was found for high CD3 (OR, 3.643), low BTLA (OR, 0.362) and high CD163 (OR, 2.669); results that are also in agreement with the postulated pathogenesis (Table ).…”

“…Importantly, human macrophages induce FOXP3 + Tregs via binding and rerelease of TGFB, the checkpoint inhibition. 38 Although not statistically significant, a trend of association with Figure 3 Gene Set Enrichment Analysis (GSEA) of immune markers in active ulcerous colitis, independent series GSE38713, versus normal mucosa. (a) Based on the markers analyzed by immunohistochemistry in this study a protein-protein network analysis was created using STRING.…”

TGF-β Affects the Differentiation of Human GM-CSF+ CD4+ T Cells in an Activation- and Sodium-Dependent Manner

“…Nevertheless these TGF-β + retinoic acid + rapamycin iTregs did not suppress in a, though artificial, xenogeneic in vivo suppression assay (34), highlighting the complexity of assays for determining iTreg suppressive function. A major complication with assays using human iTregs is that these cells lack epigenetic demethylation in the so-called Treg-specific demethylated region (TSDR) in the FOXP3 locus (56, 57) and hence lose FOXP3 upon restimulation (34, 58). Therefore, it would be complicated to study whether GM-CSF + FOXP3 + cells would lose GM-CSF upon restimulation in analogy to the murine system in Ref.…”