Article

T cell receptor signal strength in Treg and iNKT cell development demonstrated by a novel fluorescent reporter mouse

Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55414, USA.
Journal of Experimental Medicine (Impact Factor: 13.91). 06/2011; 208(6):1279-89. DOI: 10.1084/jem.20110308
Source: PubMed

ABSTRACT The ability of antigen receptors to engage self-ligands with varying affinity is crucial for lymphocyte development. To further explore this concept, we generated transgenic mice expressing GFP from the immediate early gene Nr4a1 (Nur77) locus. GFP was up-regulated in lymphocytes by antigen receptor stimulation but not by inflammatory stimuli. In T cells, GFP was induced during positive selection, required major histocompatibility complex for maintenance, and directly correlated with the strength of T cell receptor (TCR) stimulus. Thus, our results define a novel tool for studying antigen receptor activation in vivo. Using this model, we show that regulatory T cells (T(reg) cells) and invariant NKT cells (iNKT cells) perceived stronger TCR signals than conventional T cells during development. However, although T(reg) cells continued to perceive strong TCR signals in the periphery, iNKT cells did not. Finally, we show that T(reg) cell progenitors compete for recognition of rare stimulatory TCR self-ligands.

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    • "Furthermore, these T cells could produce IL-17A (Figure 1D), a cytokine that previous studies identified as pathogenic in autoimmune uveitis (Chi et al., 2008; Luger et al., 2008; Wang et al., 2012). To directly visualize the activation in vivo, we crossed the R161H mice to Nr4a1 GFP reporter mice, in which intensity of GFP fluorescence reflects the level of Nur77 expression, and hence the strength of antigen receptor signaling (Moran et al., 2011). As early as 17 days of age, and well before clinical onset of disease, GFP signal in freshly explanted intestinal tissue of R161H-Nr4a1 GFP mice was prominent , especially in the ileum, compared to ''polyclonal'' Nr4a1 GFP controls (Figure 1E and Movies S1 and S2) and was similar in intensity to the signal in adult R161H mice (Figure 1F and Movies S3 and S4). "
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    ABSTRACT: Activated retina-specific T cells that have acquired the ability to break through the blood-retinal barrier are thought to be causally involved in autoimmune uveitis, a major cause of human blindness. It is unclear where these autoreactive T cells first become activated, given that their cognate antigens are sequestered within the immune-privileged eye. We demonstrate in a novel mouse model of spontaneous uveitis that activation of retina-specific T cells is dependent on gut commensal microbiota. Retina-specific T cell activation involved signaling through the autoreactive T cell receptor (TCR) in response to non-cognate antigen in the intestine and was independent of the endogenous retinal autoantigen. Our findings not only have implications for the etiology of human uveitis, but also raise the possibility that activation of autoreactive TCRs by commensal microbes might be a more common trigger of autoimmune diseases than is currently appreciated. Copyright © 2015 Elsevier Inc. All rights reserved.
    Immunity 08/2015; 43(2):343-53. DOI:10.1016/j.immuni.2015.07.014 · 19.75 Impact Factor
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    • "Retinoids induce both Nur77-dependent transcription and the appearance of Bcl-2/BH3 domain in the DP thymocytes Previous studies have shown that retinoids induce apoptosis primarily in double positive (DP) thymocytes [12], but the basal expression of Nur77 shows a differentiation-dependence [49]. While in DP thymocytes the expression of Nur77 is low, both positive and negative selection induces the expression of Nur77, the expression correlating with the strength of the TCR signal. "
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    ABSTRACT: Nur77 is a transcription factor, which plays a determinant role in mediating T cell receptor-induced cell death of thymocytes. In addition to regulation of transcription, Nur77 contributes to apoptosis induction by targeting mitochondria, where it can convert Bcl-2, an anti-apoptotic protein into a proapoptotic molecule. Previous studies have demonstrated that retinoids are actively produced in the mouse thymus and can induce a transcription-dependent apoptosis in mouse thymocytes. Here we show that retinoic acids induce the expression of Nur77, and retinoid-induced apoptosis is completely dependent on Nur77, as retinoids were unable to induce apoptosis in Nur77 null thymocytes. In wild-type thymocytes retinoids induced enhanced expression of the apoptosis-related genes FasL, TRAIL, NDG-1, Gpr65 and Bid, all of them in a Nur77-dependent manner. The combined action of these proteins led to Caspase 8-dependent Bid cleavage in the mitochondria. In addition, we could demonstrate the Nur77-dependent induction of STAT1 leading to enhanced Bim expression, and the mitochondrial translocation of Nur77 leading to the exposure of the Bcl-2/BH3 domain. The retinoid-induced apoptosis was dependent on both Caspase 8 and STAT1. Our data together indicate that retinoids induce a Nur77-dependent cell death program in thymocytes activating the mitochondrial pathway of apoptosis. Copyright © 2014. Published by Elsevier B.V.
    Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 01/2015; 1853(3). DOI:10.1016/j.bbamcr.2014.12.035 · 5.30 Impact Factor
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    • "These observations suggested that protective class II molecules promote the differentiation of potentially pathogenic autoreactive thymocytes into Treg cells, which would then be able to effectively blunt all other autoreactive T-cell responses by suppressing autoantigen presentation in the draining lymph nodes (38, 39). Furthermore, consistent with the model of agonist selection, such increases in MHC class II-induced autoreactive Treg selection coincided with the up-regulation of CD5, CD69, and Nur77 on thymocytes, which are induced by high affinity pMHC:T-cell interactions (49), and were paralleled by negative selection (38). Expression of sub-tolerogenic, but still anti-diabetogenic class II variants in these autoreactive TCR-transgenic NOD mice promoted increases in the in vivo regulatory capacity of the peripheral Treg cell pool, owing to increases in the peripheral frequency of autoreactive regulatory T-cell specificities, further substantiating the above observations (39). "
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