The Cytokine Receptor IL-7Rα Impairs IL-2 Receptor Signaling and Constrains the In Vitro Differentiation of Foxp3+ Treg Cells

Abstract

Summary IL-7 receptor signaling is essential for the generation and maintenance of conventional T cells. Immunosuppressive Foxp3 + Treg cells, however, express uniquely low amounts of the IL-7-proprietary IL-7Rα so that they are impaired in IL-7 signaling. Because Treg cells depend on IL-2, the loss of IL-7Rα has been considered irrelevant for Treg cells. In contrast, here, we report that IL-7Rα downregulation is necessary to maximize IL-2R signaling. Although IL-7Rα overexpression promoted IL-7 signaling, unexpectedly, IL-2 signaling was suppressed in the same cells. Mechanistically, we found that γc, which is a receptor subunit shared by IL-7R and IL-2R, directly binds and pre-associates with IL-7Rα, thus limiting its availability for IL-2R binding. Consequently, overexpression of signaling-deficient, tailless IL-7Rα proteins inhibited IL-2R signaling, demonstrating that IL-7Rα sequesters γc and suppresses IL-2R signaling by extracellular interactions. Collectively, these results reveal a previously unappreciated regulatory mechanism of IL-2 receptor signaling that is governed by IL-7Rα abundance.

Assessing IL-2-Induced STAT5 Phosphorylation in Fixed, Permeabilized Foxp3+ Treg Cells by Multiparameter Flow Cytometry

“…IL-2 stimulation will result in increased levels of pSTAT5 in Foxp3 + CD4 T cells, but not in Foxp3-negative conventional CD4 T cells. As previously reported ( Cho et al., 2010 ; Keller et al., 2020 ; Waickman et al., 2020 ), conventional CD4 T cells express only low levels of IL-2Rβ and they are poor responders to IL-2. Foxp3 + Treg cells, on the other hand, express large amounts of IL-2 receptors and they are highly effective in responding to IL-2.…”

“…However, the frequency of pSTAT5-positive cells dramatically increases in Foxp3 + CD25 + Treg cells upon stimulation with increasing concentrations of IL-2. Conventional CD4 T cells, on the other hand, remain unresponsive to IL-2, as previously described ( Cho et al., 2010 ; Waickman et al., 2020 ). The percentages of pSTAT5-positive cells are then determined for each IL-2 dilution (i.e., 1 ng/mL, 0.3 ng/mL etc.)…”

“…The current protocol resolves these issues by describing a procedure to assess IL-2-induced pSTAT5 contents in Foxp3 + CD4 Treg cells using multiparameter flow cytometry. For complete details on the use and execution of this protocol, please refer to Waickman et al. (2020) .…”

“…For complete details on the use and execution of this protocol, please refer to Waickman et al. (2020) .…”

Human Adipose Tissue-Derived Mesenchymal Stromal Cells Inhibit CD4+ T Cell Proliferation and Induce Regulatory T Cells as Well as CD127 Expression on CD4+CD25+ T Cells

“…Yet, there are discrepant findings on IL-7-mediated effects on CD127±FoxP3± subpopulations. IL-7 has been reported to favor the formation of Treg [ 54 ] but also to limit their in vitro differentiation [ 55 ] and to inhibit the suppressive function of conventional Treg in favor of memory conventional T cells (CD4+CD25 low CD45RO+FoxP3-) [ 56 ]. Importantly, our study points out a novel effect of ASC on the dynamics of the CD4+ T cell compartment.…”