IFN‐γ and IL‐12 synergize to convert in vivo generated Th17 into Th1/Th17 cells

Abstract

Th1 and Th17 cells are distinct lineages of effector/memory cells, imprinted for reexpression of , by upregulated expression of T-bet and retinoic acid-related orphan receptor ct (RORct) , respectively. Apparently, Th1 and Th17 cells share tasks in the control of inflammatory immune responses. Th cells coexpressing IFN-c and IL-17 have been observed in vivo, but it remained elusive, how these cells had been generated and whether they represent a distinct lineage of Th differentiation. It has been shown that ex vivo isolated Th1 and Th17 cells are not interconvertable by TGF-b/IL-6 and IL-12, respectively. Here, we show that ex vivo isolated Th17 cells can be converted into Th1/Th17 cells by combined IFN-c and IL-12 signaling. IFN-c is required to upregulate expression of the IL-12Rb2 chain, and IL-12 for Th1 polarization. These Th1/Th17 cells stably coexpress RORct and T-bet at the single-cell level. Our results suggest a molecular pathway for the generation of Th1/Th17 cells in vivo, which combine the pro-inflammatory potential of Th1 and Th17 cells. IntroductionTh1 cells, with a memory for IFN-g expression and determined by the master transcription factor T-bet, are considered to be essential for protection against intracellular pathogens, and had been viewed as the major pathogenic drivers of chronic autoimmune inflammation, e.g. EAE [1][2][3], uveitis [4] or colitis [5]. Recently, Th17 cells, with a memory for expression of IL-17 and determined by the transcription factor retinoic acid related orphan receptor gt (RORgt), have been identified as another pathogenic Th-cell lineage driving pathogenesis in these autoimmune models [6,7]. Th17 cells contribute to inflammation through the recruitment of neutrophils and the induction of secretion of pro-inflammatory mediators such as IL-6, IL-8, TNF-a, IL-1b, CXCL1, CXCL10 and matrix metalloproteinases from tissue cells (reviewed in [8]). Th1 cells contribute to inflammation by activation of macrophages [9]. The concerted action of IFN-g and IL-17 has been shown to be essential in the effective induction and maintenance of autoimmunity [10,11], e.g. Th1 cells being required for the recruitment of Th17 cells into the central nervous system in EAE.In inflamed tissue of autoimmune patients, Th cells coexpressing IFN-g and IL-17 have been identified [12][13][14].Ã These authors have contributed equally to this study. ResultsIn vivo, Th17 cells do not express IL-12Rb2 and do not respond to IL-12Although IL-17-expressing cells isolated from cultures stimulated in vitro respond to subsequent stimulation with IL-12 with gain of IFN-g expression and loss of IL-17 expression (Fig. 1A, upper panel), IL-17 expressing cells directly isolated ex vivo maintained IL-17 expression and could not be induced to express IFN-g in the presence of IL-12 (Fig. 1A, lower panel) [17,19]. To identify the molecular mechanism of refraction of in vivo generated Th17 cells to conversion by IL-12, we here compared the expression of genes relevant for IL-12 signaling by Th17 cells generated in vit...

IL‐4‐induced gene 1 maintains high Tob1 expression that contributes to TCR unresponsiveness in human T helper 17 cells

“…Moreover, a subset of human IL-17A-producing CD4 + T cells was found to also produce IFN-γ (Th17/Th1) and both Th17 and Th17/Th1 cells exhibit plasticity toward the Th1 profile when cultured in the presence of IL-12 [4]. Similar findings were also reported in some murine models [5][6][7] suggesting that both human and murine Th17 cells probably represent a transient phenotype [8]. We have also shown that virtually all human memory Th17 cells are contained within the CD161 + fraction of both circulating and tissue-infiltrating CD4 + T cells, and originate from CD161 + precursors present in umbilical cord blood and newborn thymus [9].…”

Interleukin-23 and T helper 17-type responses in intestinal inflammation: from cytokines to T-cell plasticity

“…Hence, Bending et al 85 have shown that in-vitro-generated Th17 lymphocytes express IL-12Rb2 and are responsive to IL-12, whereas in-vivo-derived Th17 cells lack this IL-12R subunit. 88,92 Subsequent studies have shown that ex vivo Th17 cells can be converted to Th1-like cells in vitro following IFN-c-induced up-regulation of T-bet and acquisition of IL-12Rb2 88,92 (Fig. 2).…”

“…IFN-c). This Th17 phenotype instability was discovered initially using TCR transgenic CD4 + T cells polarized in vitro towards Th17 cells, [83][84][85][86] and more recently with highly purified IL-17A + or IL-17F + populations isolated by cytokine-capture assays 85,87,88 or by cell sorting based on surface expression of reporters (such as Thy-1.1, red fluorescent protein, or enhanced yellow fluorescent protein [eYFP]) that mark cells that have activated the IL-17F 84,89,90 or IL-17A 91 programme. There are some general conclusions regarding Th17 stability that can be drawn from these studies.…”

“…68 Third, the transition from Th17 cells to IFN-c-producing cells requires signal transducer and activator of transcription 4 (STAT4) and T-bet, 84 factors that are up-regulated following culture of Th17 populations with IL-12. 84,85,88,92 Experiments have also been performed to analyse the phenotype stability of in-vitro-generated Th17 cells following in vivo transfer. Hence, various Th17 populations have been given to Rag )/) or wild-type mice followed by examination of the cells at different time-points after transfer.…”

Th17 cells in systemic lupus erythematosus share functional features with Th17 cells from normal bone marrow and peripheral tissues

“…Nevertheless, a common developmental origin between human Th17 and Th1 cells has been described in various studies [4][5][6]. Accordingly, human Th17 clones appear to express IL-12Rβ2 in addition to IL-23R, and the transcription factor Tbet in addition to RORγt, as well a remarkable proportion of human Th17 cells, produces both IL-17A and IFN-γ, or human Th17 clones can be induced to produce IFN-γ and upregulate T-bet expression when cultured in the presence of IL-12 [7].…”