Seeing Is Believing: Illuminating the Source of In Vivo Interleukin-7

Interleukin-7 (IL-7) is an essential cytokine for T cells. However, IL-7 is not produced by T cells themselves such that T cells are dependent on extrinsic IL-7. In fact, in the absence of IL-7, T cell development in the thymus as well as survival of naive T cells in the periphery is severely impaired. Furthermore, modulating IL-7 availability in vivo either by genetic means or other experimental approaches determines the size, composition and function of the T cell pool. Consequently, understanding IL-7 expression is critical for understanding T cell immunity. Until most recently, however, the spatiotemporal expression of in vivo IL-7 has remained obscured. Shortage of such information was partly due to scarce expression of IL-7 itself but mainly due to the lack of adequate reagents to monitor IL-7 expression in vivo. This situation dramatically changed with a recent rush of four independent studies that describe the generation and characterization of IL-7 reporter mice, all utilizing bacterial artificial chromosome transgene technology. The emerging consensus of these studies confirmed thymic stromal cells as the major producers of IL-7 but also identified IL-7 reporter activities in various peripheral tissues including skin, intestine and lymph nodes. Strikingly, developmental and environmental cues actively modulated IL-7 reporter activities in vivo suggesting that IL-7 regulation might be a new mechanism of shaping T cell development and homeostasis. Collectively, the availability of these new tools opens up new venues to assess unanswered questions in IL-7 biology in T cells and beyond

Interleukin-7 and interleukin-15 drive CD4+CD28null T lymphocyte expansion and function in patients with acute coronary syndrome.

AIMS: Inflammation has important roles in atherosclerosis. CD4+CD28null (CD28null) T cells are a specialised T lymphocyte subset that produce inflammatory cytokines and cytotoxic molecules. CD28null T cells expand preferentially in patients with acute coronary syndrome (ACS) rather than stable angina and are barely detectable in healthy subjects. Importantly, ACS patients with CD28null T cell expansion have increased risk for recurrent acute coronary events and poor prognosis, compared to ACS patients in whom this cell subset does not expand. The mechanisms regulating CD28null T cell expansion in ACS remain elusive. We therefore investigated the role of cytokines in CD28null T cell expansion in ACS. METHODS AND RESULTS: High-purity sorted CD4+ T cells from ACS patients were treated with a panel of cytokines (TNF-α, IL-1β, IL-6, IL-7, IL-15), and effects on the number, phenotype and function of CD28null T cells were analysed and compared to the control counterpart CD28+ T cell subset. IL-7 and IL-15 induced expansion of CD28null T cells from ACS patients, while inflammatory cytokines TNF-α, IL-1β and IL-6 did not. The mechanisms underlying CD28null T cell expansion by IL-7/IL-15 were preferential activation and proliferation of CD28null T cells compared to control CD28+ T cells. Additionally, IL-7/IL-15 markedly augmented CD28null T cell cytotoxic function and interferon-γ production. Further mechanistic analyses revealed differences in baseline expression of component chains of IL-7/IL-15 receptors (CD127 and CD122) and increased baseline STAT5 phosphorylation in CD28null T cells from ACS patients compared to the control CD28+ T cell subset. Notably, we demonstrate that CD28null T cell expansion was significantly inhibited by Tofacitinib, a selective JAK1/JAK3 inhibitor that blocks IL-7/IL-15 signalling. CONCLUSIONS: Our novel data show that IL-7 and IL-15 drive the expansion and function of CD28null T cells from ACS patients suggesting that IL-7/IL-15 blockade may prevent expansion of these cells and improve patient outcomes. TRANSLATIONAL PERSPECTIVE: CD28null T cells expansion in ACS patients is an independent predictor of future acute coronary events and poor prognosis. The precise mechanisms underlying CD28null T cell expansion in ACS remain elusive. We show that IL-7 and IL-15 cytokines cause expansion of CD28null T cells from ACS patients by triggering activation and proliferation, and augment the cytotoxic function of these cells and production of inflammatory cytokines. We demonstrate that CD28null T cell expansion is inhibited by Tofacitinib that specifically blocks IL-7/IL-15 signalling. Further dissection of the roles of IL-7/IL-15 may lead to more effective and specific anti-inflammatory therapies in ACS

The transcription factor Ets1 is important for CD4 repression and Runx3 up-regulation during CD8 T cell differentiation in the thymus

The transcription factor Ets1 contributes to the differentiation of CD8 lineage cells in the thymus, but how it does so is not understood. In this study, we demonstrate that Ets1 is required for the proper termination of CD4 expression during the differentiation of major histocompatability class 1 (MHC I)–restricted thymocytes, but not for other events associated with their positive selection, including the initiation of cytotoxic gene expression, corticomedullary migration, or thymus exit. We further show that Ets1 promotes expression of Runx3, a transcription factor important for CD8 T cell differentiation and the cessation of Cd4 gene expression. Enforced Runx3 expression in Ets1-deficient MHC I–restricted thymocytes largely rescued their impaired Cd4 silencing, indicating that Ets1 is not required for Runx3 function. Finally, we document that Ets1 binds at least two evolutionarily conserved regions within the Runx3 gene in vivo, supporting the possibility that Ets1 directly contributes to Runx3 transcription. These findings identify Ets1 as a key player during CD8 lineage differentiation and indicate that it acts, at least in part, by promoting Runx3 expression

Visualization and Identification of IL-7 Producing Cells in Reporter Mice

Interleukin-7 (IL-7) is required for lymphocyte development and homeostasis although the actual sites of IL-7 production have never been clearly identified. We produced a bacterial artificial chromosome (BAC) transgenic mouse expressing ECFP in the Il7 locus. The construct lacked a signal peptide and ECFP (enhanced cyan fluorescent protein ) accumulated inside IL-7-producing stromal cells in thoracic thymus, cervical thymus and bone marrow. In thymus, an extensive reticular network of IL-7-containing processes extended from cortical and medullary epithelial cells, closely contacting thymocytes. Central memory CD8 T cells, which require IL-7 and home to bone marrow, physically associated with IL-7-producing cells as we demonstrate by intravital imaging

Visualization and Identification of IL-7 Producing Cells in Reporter Mice

Interleukin-7 (IL-7) is required for lymphocyte development and homeostasis although the actual sites of IL-7 production have never been clearly identified. We produced a bacterial artificial chromosome (BAC) transgenic mouse expressing ECFP in the Il7 locus. The construct lacked a signal peptide and ECFP (enhanced cyan fluorescent protein ) accumulated inside IL-7-producing stromal cells in thoracic thymus, cervical thymus and bone marrow. In thymus, an extensive reticular network of IL-7-containing processes extended from cortical and medullary epithelial cells, closely contacting thymocytes. Central memory CD8 T cells, which require IL-7 and home to bone marrow, physically associated with IL-7-producing cells as we demonstrate by intravital imaging

IL-10 transcription is negatively regulated by BAF180, a component of the SWI/SNF chromatin remodeling enzyme

<p>Abstract</p> <p>Background</p> <p>SWI/SNF chromatin remodeling enzymes play a critical role in the development of T helper lymphocytes, including Th2 cells, and directly program chromatin structure at Th2 cytokine genes. Different versions of SWI/SNF complexes, including BAF and PBAF, have been described based on unique subunit composition. However, the relative role of BAF and PBAF in Th cell function and cytokine expression has not been reported.</p> <p>Results</p> <p>Here we examine the role of the PBAF SWI/SNF complex in Th cell development and gene expression using mice deficient for a PBAF-specific component, BAF180. We find that T cell development in the thymus and lymphoid periphery is largely normal when the BAF180 gene is deleted late in thymic development. However, BAF180-deficient Th2 cells express high levels of the immunoregulatory cytokine IL-10. BAF180 binds directly to regulatory elements in the Il-10 locus but is replaced by BAF250 BAF complexes in the absence of BAF180, resulting in increased histone acetylation and CBP recruitment to the IL-10 locus.</p> <p>Conclusions</p> <p>These results demonstrate that BAF180 is a repressor of IL-10 transcription in Th2 cells and suggest that the differential recruitment of different SWI/SNF subtypes can have direct consequences on chromatin structure and gene transcription.</p

FOXN1 in thymus organogenesis and development

Development of the primary T‐cell repertoire takes place in the thymus. The linked processes of T‐cell differentiation and T‐cell repertoire selection each depend on interactions between thymocytes and thymic stromal cells; in particular, with the epithelial cells of the cortical and medullary thymic compartments (cortical and medullary thymic epithelial cells; cTECs and mTECs, respectively). The importance of the thymic epithelial cell lineage in these processes was revealed in part through analysis of nude (nu/nu) mice, which are congenitally hairless and athymic. The nude phenotype results from null mutation of the forkhead transcription factor FOXN1, which has emerged as a pivotal regulator both of thymus development and homeostasis. FOXN1 has been shown to play critical roles in thymus development, function, maintenance, and even regeneration, which positions it as a master regulator of thymic epithelial cell (TEC) differentiation. In this review, we discuss current understanding of the regulation and functions of FOXN1 throughout thymus ontogeny, from the earliest stages of organogenesis through homeostasis to age‐related involution, contextualising its significance through reference to other members of the wider Forkhead family

Autoimmune aspects of psoriasis: Heritability and autoantigens

Chronic immune-mediated disorders (IMDs) constitute a major health burden. Understanding IMD pathogenesis is facing two major constraints: Missing heritability explaining familial clustering, and missing autoantigens. Pinpointing IMD risk genes and autoimmune targets, however, is of fundamental importance for developing novel causal therapies. The strongest association of all IMDs is seen with human leukocyte antigen (HLA) alleles. Using psoriasis as an IMD model this article reviews the pathogenic role HLA molecules may have within the polygenic predisposition of IMDs. It concludes that disease-associated HLA alleles account for both missing heritability and autoimmune mechanisms by facilitating tissue-specific autoimmune responses through autoantigen presentation. (C) 2017 The Author. Published by Elsevier B.V

Ontogeny and regulation of interleukin-7 expressing thymic epithelial cells

T cell development is a multistage process of differentiation that depends on proper thymocyte-thymic epithelial cell (TEC) interactions. Epithelial cells in the thymus are organized in a three-dimensional network that provides support and signals for thymocyte maturation. Concurrently, proper TEC differentiation in the adult thymus relies on thymocyte-derived signals. TECs produce interleukin-7 (IL-7), a non-redundant cytokine that promotes the survival, differentiation, and proliferation of thymocytes. We have identified IL-7 expressing TECs throughout ontogeny and in the adult thymus by in situ hybridization analysis. IL-7 expression is initiated in the thymic fated domain of the thymic primordium by embryonic day 11.5, in a Foxn1 independent pathway. Marked changes occur in the localization and regulation of IL-7 expressing TECs during development. Whereas IL-7 expressing TECs are present throughout the early thymic rudiment, the majority of IL-7 producing TECs are concentrated in the adult thymic medulla. By analyzing mouse strains that sustain blocks at different stages of thymocyte development, we show that IL-7 expression is initiated independently of hematopoietic-derived signals during thymic organogenesis. However, thymocyte-derived signals play an essential role in regulating IL-7 expression in the adult TEC compartment. Furthermore, distinct thymocyte subsets regulate the expression of IL-7 and keratin 5 in adult cortical epithelium. Intraperitoneal injection of Recombination Activating Gene deficient mice (RAG-2−/−) with anti-CD3ϵ monoclonal antibody (mAb) induces CD4− 8− double negative thymocytes to undergo β-selection and differentiate into CD4+8+ cells. Analysis of the thymic stromal compartment reveals that progression through β-selection renders thymocytes competent to alter the pattern of IL-7 expression in the cortical TEC compartment. RAG-2−/− mice do not generate mature T cells and therefore the RAG-2−/− thymus is devoid of organized medullary regions. Histological examination of RAG-2−/− thymus following anti-CD3ϵ stimulation reveals the emergence of mature thymic medullary regions, as assessed by H & E staining and expression of thymic stromal medullary markers. Stromal medullary reorganization occurs in the absence of T cell receptor αβ expression, suggesting that activation of RAG-2−/− thymocytes by CD3ϵ ligation generates thymocyte-derived signals that induce thymic epithelial reorganization, generating a mature medullary compartment. This model provides a tool to assess the mechanisms underlying thymic medullary development

Spatial Memory in Captive American Black Bears (\u3ci\u3eUrsus americanus\u3c/i\u3e)

The spatial memory and foraging strategies of four adult captive-born American black bears (Ursus americanus) were explored in four experiments using a simulated foraging task. In the first three experiments, each session consisted of two phases separated by a delay: During the exploration phase, subjects foraged among a set of baited and unbaited sites. During the delay, the same locations were rebaited and subjects were released again and allowed to search the sites (search phase). In Experiments 1a and 1b, different sites were baited each day and the interval between exploration and search was short (4 hr or 15 min). Subjects were not accurate at recovering the food items in either experiment. In Experiment 2, an informed forager paradigm was used in which one subject was given privileged knowledge about the location of the food during the exploration phase and was later released with an uninformed competitor during the search phase. The bears did not achieve above-chance recovery accuracy even in the presence of a competitor. In Experiment 3, the same two of four sites were continually baited and the bears were released simultaneously over a period of 20 days, with each baiting separated by 2 or 3 days. As a group, the bears\u27 foraging accuracy with repeated baiting and longer intervals approached greater than chance accuracy. Results suggest some limitations on bears\u27 use of spatial memory in captive environments, but reveal the potential for use of spatial memory over longer delays