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

Szabolcs Éliás,John Andersson,Venkateshan Kannan,Jesper Tegnér,Angelika Schmidt

doi:10.3389/fimmu.2016.00603

Abstract

The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is involved in the pathogenesis of chronic inflammatory diseases such as multiple sclerosis. However, the environmental cues promoting differentiation of GM-CSF producing T cells are unclear. Herein, we performed a broad experimental screening of cytokines and data-driven analysis assessing their ability to induce human GM-CSF+ CD4+ T cells and their subpopulations. TGF-β was discovered to induce GM-CSF production independently of proliferation and IL-2 signaling including STAT5. In contrast, IL-6 and IL-23 decreased GM-CSF production. On the population level, GM-CSF induction was highly correlated with expression of FOXP3 across cytokine stimulations but not with that of IL-17. However, on single-cell level GM-CSF and IFN-γ expression were most correlated, independently of the cytokine environment. Importantly, under low sodium conditions in the medium or upon stimulation with plate-bound instead of bead-bound anti-CD3 and anti-CD28 antibodies, the effects of TGF-β on GM-CSF, but not on FOXP3, were reversed. Our analysis indicates a novel role for TGF-β in generating GM-CSF+ subsets of human CD4+ T cells. These results are important for understanding of autoimmune disease and therapeutic considerations.

Highlights

CD4+ T cells are central in directing immune responses and have been implicated in numerous diseases such as chronic inflammation, cancer, and neurodegenerative diseases
To investigate conditions for induction of granulocyte-macrophage colony-stimulating factor (GM-CSF)+ cells, we cultured human naïve CD4+ T cells in the presence of (i) IL-6, IL-21, and TGF-β1 that have been shown to be involved in the induction of IL-17+ cells [27,28,29], (ii) IL-1β, IL-23, and TGF-β3 that have been proposed to induce murine “pathogenic” GM-CSF+IL-17+ cells [11, 14,15,16], and (iii) IL-2 that has been reported to induce human GM-CSF+ CD4+ T cells [5, 9]
The cells were activated with anti-CD3, anti-CD28-coated beads for 5–6 days, and GM-CSF expression was measured by intracellular flow cytometry

Summary

Introduction

CD4+ T cells are central in directing immune responses and have been implicated in numerous diseases such as chronic inflammation, cancer, and neurodegenerative diseases. CD4+ T cells can be classified as effector T helper (Th) cells and immunosuppressive regulatory T cells (Treg). Th cells can be further divided into the major subsets Th1, Th2, and Th17 cells, based on their cytokine profile such as expression of IFN-γ, IL-4, and IL-17 that is driven largely by expression of the lineage-defining transcription factors T-bet, GATA-3, and RORγt, respectively [1]. The most important Treg subset, comprised of thymus-derived and peripherally induced Tregs, is characterized by expression of the lineage-defining transcription factor FOXP3 [2]. Recent investigations revealed numerous subsets as well as plasticity in the CD4+ T cell population beyond the classical distinction between. Th1, Th2, Th17, and Treg [3, 4]. Th9, Th22, Tfh, Tfr have been described as additional subpopulations [1]

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