Mucosal antibody responses play a major role in mediating homeostasis with the intestinal flora. It has been suggested that imbalance in the IgA + and IgG + intestinal B cell repertoire may be associated with the development of diseases such as inflammatory bowel disease. Despite this, little is known about the antibody specificity of human intestinal plasmablasts. Here, we have determined the reactivity profile of single isolated IgA + and IgG + plasmablasts from human terminal ileum using antibody cloning and in vitro expression. We found that approximately 25% of intestinal IgA and IgG plasmablast antibodies were polyreactive; the majority were antigen-specific. Antigen specificity was not only directed against enteropathogenic microbes but also against commensal microbes and self antigens. Regardless of their reactivity, all intestinal antibodies were somatically mutated and showed signs of antigen-mediated selection, suggesting that they developed from antigen-specific B cell responses. Together, our data indicate that antigen-specific immune responses to intestinal microbes are largely responsible for the maintenance of intestinal homeostasis and thus provide a basis for understanding the deregulated immune responses observed in patients with inflammatory bowel disease.

Two distinct subsets of γδ T cells that produce interleukin 17 (IL-17) (CD27 − γδ T cells) or interferon-γ (IFN-γ) (CD27 + γδ T cells) develop in the mouse thymus, but the molecular determinants of their functional potential in the periphery remain unknown. Here we conducted a genome-wide characterization of the methylation patterns of histone H3, along with analysis of mRNA encoding transcription factors, to identify the regulatory frames of peripheral IFN-γ-producing or IL-17-producing γδ T cell subsets in vivo. We found that CD27 + γδ T cells were committed to the expression of Ifng but not Il17, whereas CD27 − γδ T cells displayed permissive chromatin configurations at loci related to both the T H 17 and T H 1 subsets of helper T cells and differentiated into cells producing both IL-17 and IFN-γ in a tumor microenvironment.γδ T cells have emerged as key providers of interleukin 17 (IL-17) in various models of infection, inflammation and autoimmunity [1][2][3][4][5][6] . Antibody-mediated or genetic depletion of γδ T cells greatly reduces disease severity in IL-17-driven models of chronic inflammation [1][2][3][4]7 . Those results notwithstanding, many reports have made a compelling case for γδ T cells as the main producers of interferon-γ (IFN-γ) in both mice and humans 8 , which has been a major foundation for clinical trials targeting these lymphocytes in cancer immunotherapy 9 . Given the dual ability of γδ cells to produce IL-17 and IFN-γ, published work has aimed to contributed to designing the study and writing the manuscript; A.Q.G. helped to design and supervise the study; and B.S.-S. designed and supervised the study and wrote the manuscript. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests.Reprints and permissions information is available online at http://www.nature.com/reprints/index.html. Europe PMC Funders GroupAuthor Manuscript Nat Immunol. Author manuscript; available in PMC 2016 April 18. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts identify markers that associate with functional attributes of mouse γδ T cells [10][11][12][13] . Expression of the costimulatory receptor CD27 segregates IL-17-producing (CD27 − ) γδ T cells and IFN-γ-producing (CD27 + ) γδ T cells in both naive and Plasmodium-infected C57BL/6 mice 10 . Moreover, the chemokine receptor CCR6, which is expressed exclusively on CD27 − γδ T cells, constitutes an additional marker for IL-17 + γδ T cells 13,14. Both CD27 + and CD27 − γδ T cell subsets show spontaneous cytokine secretion after activation, in contrast to the delayed differentiation of conventional CD4 + T cells of the T H 1 or T H 17 subset of helper T cells 15 . That finding is highlighted by the observation that 30-40% of peripheral γδ T cells freshly isolated from naive mice produce either IL-17 or IFN-γ after 3 h of restimulation in vitro 10 . Those functionally mature γδ T cell subsets are also found in the thymus, as early as the embryonic stages of mouse development [10][11][12]16 . Moreove...

Chromatin modifications regulate genome function by recruiting protein factors to the genome. However, the protein composition at distinct chromatin modifications remains to be fully characterized. Here, we use natural protein domains as modular building blocks to develop engineered chromatin readers (eCRs) selective for DNA methylation and histone tri-methylation at H3K4, H3K9 a H3K27 residues. We first demonstrate their utility as selective chromatin binders in living cells by stably expressing eCRs in mouse embryonic stem cells and measuring their subnuclear localisation, genomic distribution and histone modification–binding preference. By fusing eCRs to the biotin ligase BASU, we establish ChromID, a method for identifying the chromatin-dependent protein interactome based on proximity biotinylation, and apply it to distinct chromatin modifications in mouse stem cells. Using a synthetic dual-modification reader, we also uncover the protein composition at bivalent promoters marked by H3K4me3 and H3K27me3. These results highlight the ability of ChromID to obtain a detailed view of protein interaction networks on chromatin.

Pro‐inflammatory interleukin (IL)‐17‐producing γδ (γδ17) T cells are thought to develop exclusively in the thymus during fetal/perinatal life, as adult bone marrow precursors fail to generate γδ17 T cells under homeostatic conditions. Here, we employ a model of experimental autoimmune encephalomyelitis (EAE) in which hematopoiesis is reset by bone marrow transplantation and demonstrate unequivocally that Vγ4+ γδ17 T cells can develop de novo in draining lymph nodes in response to innate stimuli. In vitro, γδ T cells from IL‐17 fate‐mapping reporter mice that had never activated the Il17 locus acquire IL‐17 expression upon stimulation with IL‐1β and IL‐23. Furthermore, IL‐23R (but not IL‐1R1) deficiency severely compromises the induction of γδ17 T cells in EAE, demonstrating the key role of IL‐23 in the process. Finally, we show, in a composite model involving transfers of both adult bone marrow and neonatal thymocytes, that induced γδ17 T cells make up a substantial fraction of the total IL‐17‐producing Vγ4+ T‐cell pool upon inflammation, which attests the relevance of this novel pathway of peripheral γδ17 T‐cell differentiation.

γδ T lymphocytes are programmed into distinct IFN-γ–producing CD27+ (γδ27+) and IL-17–producing CD27− (γδ27−) subsets that play key roles in protective or pathogenic immune responses. Although the signature cytokines are shared with their αβ Th1 (for γδ27+) and Th17 (for γδ27−) cell counterparts, we dissect in this study similarities and differences in the transcriptional requirements of murine effector γδ27+, γδ27−CCR6−, and γδ27−CCR6+ γδ T cell subsets and αβ T cells. We found they share dependence on the master transcription factors T-bet and RORγt for IFN-γ and IL-17 production, respectively. However, Eomes is fully dispensable for IFN-γ production by γδ T cells. Furthermore, the Th17 cell auxiliary transcription factors RORα and BATF are not required for IL-17 production by γδ27− cell subsets. We also show that γδ27− (but not γδ27+) cells become polyfunctional upon IL-1β plus IL-23 stimulation, cosecreting IL-17A, IL-17F, IL-22, GM-CSF, and IFN-γ. Collectively, our in vitro and in vivo data firmly establish the molecular segregation between γδ27+ and γδ27− T cell subsets and provide novel insight on the nonoverlapping transcriptional networks that control the differentiation of effector γδ versus αβ T cell subsets.

microRNA (miRNA) mediated regulation of protein expression has emerged as an important mechanism in T-cell physiology, from development and survival to activation, proliferation, and differentiation. One of the major classes of proteins involved in these processes are cytokines, which are both key input signals and major products of T-cell function. Here, we summarize the current data on the molecular cross-talk between cytokines and miRNAs: how cytokines regulate miRNA expression, and how specific miRNAs control cytokine production in T cells. We also describe the inflammatory consequences of deregulating the miRNA/cytokine axis in mice and humans. We believe this topical area will have key implications for immune modulation and treatment of autoimmune pathology. Keywords:Cytokines r Inflammation r miRNA r T cells microRNAs as regulators of protein expressionBiological processes require the integration of environmental stimuli at the level of gene expression. The robustness of genetic networks depends on the distinction between physiological responses (to particular cues) and biological "noise" (stochastic variations), which can be achieved, for example, by establishing feed-forward transcriptional loops. Over the past two decades, a new mechanism that interacts with transcriptional loops and sets additional thresholds, which enable cells to filter physiological signals from noise has emerged; this mechanism regulates gene expression at the posttranscriptional level and relies on microRNAs (miRNAs; reviewed in [1]). These are an abundant class of evolutionarily conserved small noncoding (untranslated) RNA species that control target mRNA stability, degradation, and translation, thus affecting the majority of mammalian genes [2].Correspondence: Dr. Anita Q. Gomes e-mail: anitagomes@medicina.ulisboa.ptIn the conventional miRNA biogenesis pathway, RNA polymerase II transcribed pri-miRNAs are processed by the nuclear RNase III enzyme Drosha (complexed with DGCR8) to generate 60-70 nt stem-loop intermediates, the pre-miRNAs, that are further processed into 19-24mers in the cytoplasm by another key RNase III, Dicer. Mature miRNAs are then incorporated into RNAinduced silencing complexes, whose core components are proteins of the Argonaute family (Ago1-4), which use the 5 end (nucleotides 2-8) "seed sequence" of the miRNA to recognize complementary mRNA transcripts (mostly in their 3 untranslated region) for deadenylation or inhibition of translation, ultimately resulting in mRNA decapping and decay (reviewed in [3,4]).Unique spatial and temporal expression patterns in distinct hematopoietic cell lineages are suggestive of multiple roles for miRNAs in hematopoiesis, self-tolerance, and in immune responses, which have been explored over the past decade (reviewed in [5,6]). Over a 100 different miRNAs have been shown to be expressed by cells of the immune system, where * These authors contributed equally to this work as first authors. * * These authors contributed equally to this work as last authors.C 2015 WILEY-VCH Ve...

Chemotherapy-resistant cancer recurrence is a major cause of mortality. In acute myeloid leukemia (AML), chemorefractory relapses result from the complex interplay between altered genetic, epigenetic and transcriptional states in leukemic cells. Here, we develop an experimental model system using in vitro lineage tracing coupled with exome, transcriptome and in vivo functional readouts to assess the AML population dynamics and associated molecular determinants underpinning chemoresistance development. We find that combining standard chemotherapeutic regimens with low doses of DNA methyltransferase inhibitors (DNMTi, hypomethylating drugs) prevents chemoresistant relapses. Mechanistically, DNMTi suppresses the outgrowth of a predetermined set of chemoresistant AML clones with stemness properties, instead favoring the expansion of rarer and unfit chemosensitive clones. Importantly, we confirm the capacity of DNMTi combination to suppress stemnessdependent chemoresistance development in xenotransplantation models and primary AML patient samples. Together, these results support the potential of DNMTi combination treatment to circumvent the development of chemorefractory AML relapses.

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