Project description:Thymic stromal lymphopoietin (TSLP) is a type I cytokine that promotes allergic responses and mediates type 2 immunity. A balance between effector T cells (Teff), which drive the immune response, and regulatory T cells (Tregs), which suppress the response, is required for proper immune homeostasis. Here, we report that TSLP differentially acts on Teff versus Tregs to balance type 2 immunity. As expected, deletion of TSLPR on all T cells (Cd4CreCrlf2fl/fl mice) resulted in lower numbers of Th2 cells and diminished ovalbumin-induced airway inflammation, but selective deletion of TSLPR on Tregs (Foxp3YFP-Cre/YCrlf2fl/fl mice) resulted in increased IL-5- and IL-13-secreting Th2 cells and lung eosinophilia. Moreover, TSLP augmented the expression of factors that stabilize Tregs, and remarkably, during type 2 immune responses, TSLPR-deficient Tregs acquired Th2-like properties, with augmented levels of GATA3 and secretion of IL-13. Thus, TSLP not only is a driver of Th2 effector cells, but it also acts in a negative feedback loop, promoting the ability of Tregs to limit allergic inflammation.
Project description:Thymic stromal lymphopoietin (TSLP) is a type I cytokine that promotes allergic responses and mediates type 2 immunity. A balance between effector T cells (Teff), which drive the immune response, and regulatory T cells (Tregs), which suppress the response, is required for proper immune homeostasis. Here, we report that TSLP differentially acts on Teff versus Tregs to balance type 2 immunity. As expected, deletion of TSLPR on all T cells (Cd4CreCrlf2fl/fl mice) resulted in lower numbers of Th2 cells and diminished ovalbumin-induced airway inflammation, but selective deletion of TSLPR on Tregs (Foxp3YFP-Cre/YCrlf2fl/fl mice) resulted in increased IL-5- and IL-13-secreting Th2 cells and lung eosinophilia. Moreover, TSLP augmented the expression of factors that stabilize Tregs. During type 2 immune responses, TSLPR-deficient Tregs acquired Th2-like properties, with augmented GATA3 expression and secretion of IL-13. TSLP is not only a driver of Th2 effector cells but also acts in a negative feedback loop, thus promoting the ability of Tregs to limit allergic inflammation.
Project description:Thymic stromal lymphopoietin (TSLP) is a type I cytokine that plays a central role in induction of allergic inflammatory responses. Its principal targets have been reported to be dendritic cells and / or CD4 T cells; epithelial cells are a principal source. We report here the development of a reporter mouse (TSLP-ZsG) in which a ZsGreen (ZsG)-encoding construct has been inserted by recombineering into a bacterial artificial chromosome (BAC) immediately at the translation initiating ATG of TSLP. The expression of ZsG by mice transgenic for the recombinant BAC appears to be a faithful surrogate for TSLP expression, particularly in keratinocytes and medullary thymic epithelials cells (mTECs). A comparison of gene expression in ZsG expressing and ZsG negative mTECs and cortical thymic epithelial cells, which are all ZsG negative, revealed that all three populations can be distinguished from one another. In particular ZsG (and TSLP) expressing mTECs and ZsG- mTECs are separable populations based on gene expression profiling. Little or no expression of ZsG is observed in bone marrow-derived mast cells or basophils or in CD45+ cells infiltrating TSLP/ZsG-expressing skin. Using the TSLP-ZsG reporter mouse, we show that TNFa and IL-4/IL-13 are potent inducers of TSLP expression by keratinocytes and that local activation of Th2 and Th1 cells induces keratinocyte TSLP expression. We suggest that the capacity of TSLP to both induce Th2 differentiation and to be induced by activated Th2 cells raises the possibility that TSLP may be involved in a positive feedback loop to enhance allergic inflammatory conditions.
Project description:Staphylococcus aureus can cause serious skin, respiratory, and other life-threatening invasive infections in humans, and methicillin-resistant S. aureus (MRSA) strains have been acquiring increasing antibiotic resistance. While MRSA was once mainly considered a hospital-acquired infection, the emergence of new strains, some of which are pandemic, has resulted in community-acquired MRSA infections that often present as serious skin infections in otherwise healthy individuals. Accordingly, defining the mechanisms that govern the activation and regulation of the immune response to MRSA is clinically important and could lead to the discovery of much needed rational targets for therapeutic intervention. Because the cytokine thymic stromal lymphopoetin (TSLP) is highly expressed by keratinocytes of the skin3, we investigated its role in host-defense against MRSA. Here we demonstrate that TSLP acts on neutrophils to increase their killing of MRSA. In particular, we show that both mouse and human neutrophils express functional TSLP receptors. Strikingly, TSLP enhances mouse neutrophil killing of MRSA in both an in vitro whole blood killing assay and an in vivo skin infection model. Similarly, TSLP acts directly on purified human blood neutrophils to reduce MRSA burden. Unexpectedly, we demonstrate that TSLP mediates these effects both in vivo and in vitro by engaging the complement C5 system. Thus, TSLP increases MRSA killing in a neutrophil- and complement-dependent manner, revealing a key connection between TSLP and the innate complement system, with potentially important therapeutic implications for control of MRSA infection.
Project description:Pathogenesis of allergic diseases including asthma is strongly associated with robust responses of allergen-specific Th2 cells, which produce high levels of IL-4, IL-5, IL-9, and IL-13. Despite evidence for pathogenic Th2 cells in the induction and propagation of allergic disorders, signals required for differentiation of such cells remain largely unknown. Thymic stromal lymphopoietin (TSLP) is a cytokine that is expressed upon epithelial injury, dysfunction or infection and is strongly implicated in the pathogenesis of atopic dermatitis (AD) and asthma. Although indirect regulation of Th2 differentiation via TSLP-stimulated dendritic cells well known, direct effects of TSLP on Th2 differentiation in vivo have not been rigorously analyzed. We show that TSLP may initiate Th2 response independent on IL-4 signal and increases sensitivity of CD4 cells to IL-4 stimulation inducing more robust expression of IL-4, IL-5, and IL-13 by human and mouse CD4 cells. This more potent effector state appears to be stably programmed in memory Th2 cells. As part of molecular mechanism, we demonstrate that TSLP and IL-4 signals induce distinctive genome wide alterations in activating histone modification (H3K27Ac, H3K36Me3, and H3K4Me3). We propose that TSLP acts in coordination with IL-4 to generate a more potent Th2 state that could underlie persistence and propagation of allergic disorders.
Project description:Allergic airway inflammation is a chronic inflammatory condition resulting from uncontrolled immune responses to environmental antigens. While it is well-established that allergic immune responses exhibit a high degree of diversity, driven by primary effector cell types like eosinophils, neutrophils, or CD4 T cells with distinct effector signatures, the exact mechanisms responsible for such pathogenesis remain largely elusive. Foxp3+ regulatory T cells (Treg) is an indispensable immune regulator during chronic inflammation including allergic airway inflammation. Emerging evidence suggests that Tregs infiltrating inflamed tissues exhibit distinct phenotypes dependent on the specific tissue sites and can display significant heterogeneity and tissue residency. Whether diverse allergic inflammatory responses in the lung influences infiltrating Treg heterogeneity or Treg lung residency has not previously been explored. We employed an unbiased single-cell RNAseq approach to study lung-infiltrating Tregs in models of eosinophilic and neutrophilic airway inflammation models, in which Tregs are critical immune regulators of inflammation. We found that lung-infiltrating Tregs are highly heterogeneous and that Tregs displaying lung residency phenotypes are significantly different depending on the types of inflammation. Tregs expression of ST2, a receptor for alarmin cytokine IL-33, was predominantly induced by eosinophilic inflammation and by tissue residency. However, Treg-specific ST2 deficiency did not affect the development of eosinophilic allergic inflammation nor the generation of lung resident Tregs. These results uncover a striking heterogeneity among Tregs infiltrating the lungs during allergic airway inflammation. The results also indicate that varying types of inflammation may give rise to phenotypically distinct lung resident Tregs. Thus, the present study underscores a novel mechanism by which inflammatory environments may shape the composition of infiltrating Tregs, allowing them to regulate inflammatory responses through tissue-adapted mechanisms.
Project description:Extramedullary hematopoiesis (EMH) refers to the differentiation of hematopoietic stem cells (HSCs) into effector cells that occurs in compartments outside of the bone marrow. Previous studies linked pattern recognition receptor (PRR)-expressing HSCs, EMH and immune responses to microbial stimuli. However, the factors that regulate EMH and whether EMH operates in broader immune contexts remain unknown. Here, we demonstrate a previously unrecognized role for thymic stromal lymphopoietin (TSLP) in promoting the population expansion of progenitor cells in the periphery and identify that TSLP-elicited progenitors differentiate into effector cells including macrophages, dendritic cells and granulocytes that contribute to TH2 cytokine responses. The frequency of circulating progenitor cells was also increased in allergic patients with a gain-of-function polymorphism in TSLP, suggesting the TSLP-EMH pathway may operate in human disease. These data identify that TSLP-induced EMH contributes to the development of allergic inflammation and indicate that EMH is a conserved mechanism of innate immunity. In this study, we performed gene expression profiling to examine how the transcriptional signatures compared between TSLP-elcited GMP-like cells and naïve bone marrow-resident GMPs. Splenic TSLP-elicited GMP-like cells (CD3-, CD4-, CD5-, CD8-, CD19-, CD11b-, CD11c-, NK1.1-, FcεRI-, CD34+ c-kit+) were sort-purified from the spleen of C57BL/6 mice on day 5 post-TSLP-cDNA treatment. BM-resident GMPs (CD3-, CD4-, CD5-, CD8-, CD19-, CD11b-, CD11c-, NK1.1-, FcεRI-, Sca1- c-kit+ CD34+ CD16/32+) were sort-purified from mice that received a control-cDNA injection.
Project description:TSLP is believed to play a role in allergic diseases such as atopic dermatitis and asthma, through its activation of dendritic cells which later promote the induction of inflammatory Th2 cells. We sought to characterize the inflammatory response induced by TSLP challenge in naive and OVA-sensitized mice using gene expression profiling.
Project description:Recruitment of regulatory T cells (Tregs) to tumors is a hallmark of cancer progression. However, the role of epithelial cell-derived cytokines in regulation of Treg cells in colorectal cancers is not fully understood. We found a subset of Tregs co-expressing the receptors for thymic stromal lymphopoietin (TSLP) and IL-33 (TSLPR+ST2+ Tregs) was increased in colorectal tumors in humans and mice. This Treg subset expressed high levels of CTLA-4 and PD-1, and TSLPR signaling regulated the expression of CTLA-4 and number of TSLPR+ST2+ Tregs. Treg-specfic deletion of TSLPR resulted in a reduction in tumor number and size, with concomitant increase of Th1 cells in tumors. Similarly, blockade of TSLP effectively inhibited progression of colorectal tumors. On the other hand, TSLPR-ST2+ Tregs highly express Tgfb1 and Pdcd,1 which have been shown to suppress CD8+ T cell immune responses. Collectively, TSLP and IL-33 differentially regulate subsets of Tregs in the progression of colorectal tumor. These data suggest that TSLPR+ST2+ Treg cells are potentially a biomarker, and a therapeutic target for CRC.