Precursor central memory versus effector cell fate and naïve CD4+ T cell heterogeneity.

Upon antigenic stimulation, naïve CD4+ T cells can give rise to phenotypically distinct effector T helper cells and long-lived memory T cells. We computationally reconstructed the in vivo trajectory of CD4+ T cell differentiation during a type I inflammatory immune response and identified two distinct differentiation paths for effector and precursor central memory T cells arising directly from naïve CD4+ T cells. Unexpectedly, our studies revealed heterogeneity among naïve CD4+ T cells, which are typically considered homogeneous save for their diverse T cell receptor usage.

Novel antigen-presenting cell imparts T-dependent tolerance to gut microbiota.

Establishing and maintaining tolerance to self-antigens or innocuous foreign antigens is vital for the preservation of organismal health. Within the thymus, medullary thymic epithelial cells (mTECs) expressing autoimmune regulator (AIRE) have a critical role in self-tolerance through deletion of autoreactive T cells and promotion of thymic regulatory T (T) cell development. Within weeks of birth, a separate wave of T cell differentiation occurs in the periphery upon exposure to antigens derived from the diet and commensal microbiota, yet the cell types responsible for the generation of peripheral T (pT) cells have not been identified.

T reg cell-intrinsic requirements for ST2 signaling in health and neuroinflammation.

ST2, the receptor for the alarmin IL-33, is expressed by a subset of regulatory T (T reg) cells residing in nonlymphoid tissues, and these cells can potently expand upon provision of exogenous IL-33. Whether the accumulation and residence of T reg cells in tissues requires their cell-intrinsic expression of and signaling by ST2, or whether indirect IL-33 signaling acting on other cells suffices, has been a matter of contention. Here, we report that ST2 expression on T reg cells is largely dispensable for their accumulation and residence in nonlymphoid organs, including the visceral adipose tissue (VAT), even though cell-intrinsic sensing of IL-33 promotes type 2 cytokine production by VAT-residing T reg cells.

IL-2 production by self-reactive CD4 thymocytes scales regulatory T cell generation in the thymus.

Regulatory T (T reg) cells, a specialized subset of CD4 T cells, are essential to prevent fatal autoimmunity. Expression of the T reg lineage-defining transcription factor Foxp3, and therefore their differentiation in the thymus, is dependent upon T cell receptor (TCR) and interleukin-2 (IL-2) signaling. Here, we report that the majority of IL-2-producing cells in the thymus are mature CD4 single-positive (CD4SP) thymocytes and that continuous IL-2 production sustained thymic T reg cell generation and control of systemic immune activation.

Nemo-like Kinase Drives Foxp3 Stability and Is Critical for Maintenance of Immune Tolerance by Regulatory T Cells.

The Foxp3 transcription factor is a crucial determinant of both regulatory T (T) cell development and their functional maintenance. Appropriate modulation of tolerogenic immune responses therefore requires the tight regulation of Foxp3 transcriptional output, and this involves both transcriptional and post-translational regulation. Here, we show that during T cell activation, phosphorylation of Foxp3 in T cells can be regulated by a TGF-β activated kinase 1 (TAK1)-Nemo-like kinase (NLK) signaling pathway.

Myeloid-Specific Deletion of Peptidylarginine Deiminase 4 Mitigates Atherosclerosis.

Increasing evidence suggests that neutrophil extracellular traps (NETs) may play a role in promoting atherosclerotic plaque lesions in humans and in murine models. The exact pathways involved in NET-driven atherogenesis remain to be systematically characterized. To assess the extent to which myeloid-specific peptidylarginine deiminase 4 (PAD4) and PAD4-dependent NET formation contribute to atherosclerosis, mice with myeloid-specific deletion of PAD4 were generated and backcrossed to Apoe mice.

Corrigendum: Stability and function of regulatory T cells expressing the transcription factor T-bet.

This corrects the article DOI: 10.1038/nature22360.

Stability and function of regulatory T cells expressing the transcription factor T-bet.

Adaptive immune responses are tailored to different types of pathogens through differentiation of naive CD4 T cells into functionally distinct subsets of effector T cells (T helper 1 (T1), T2, and T17) defined by expression of the key transcription factors T-bet, GATA3, and RORγt, respectively. Regulatory T (T) cells comprise a distinct anti-inflammatory lineage specified by the X-linked transcription factor Foxp3 (refs 2, 3). Paradoxically, some activated T cells express the aforementioned effector CD4 T cell transcription factors, which have been suggested to provide T cells with enhanced suppressive capacity.

Suppression of lethal autoimmunity by regulatory T cells with a single TCR specificity.

The regulatory T cell (T reg cell) T cell receptor (TCR) repertoire is highly diverse and skewed toward recognition of self-antigens. TCR expression by T reg cells is continuously required for maintenance of immune tolerance and for a major part of their characteristic gene expression signature; however, it remains unknown to what degree diverse TCR-mediated interactions with cognate self-antigens are required for these processes. In this study, by experimentally switching the T reg cell TCR repertoire to a single T reg cell TCR, we demonstrate that T reg cell function and gene expression can be partially uncoupled from TCR diversity.

Memory of Inflammation in Regulatory T Cells.

Eukaryotic cells can "remember" transient encounters with a wide range of stimuli, inducing lasting states of altered responsiveness. Regulatory T (Treg) cells are a specialized lineage of suppressive CD4 T cells that act as critical negative regulators of inflammation in various biological contexts. Treg cells exposed to inflammatory conditions acquire strongly enhanced suppressive function.

A mechanism for expansion of regulatory T-cell repertoire and its role in self-tolerance.

T-cell receptor (TCR) signalling has a key role in determining T-cell fate. Precursor cells expressing TCRs within a certain low-affinity range for complexes of self-peptide and major histocompatibility complex (MHC) undergo positive selection and differentiate into naive T cells expressing a highly diverse self-MHC-restricted TCR repertoire. In contrast, precursors displaying TCRs with a high affinity for 'self' are either eliminated through TCR-agonist-induced apoptosis (negative selection) or restrained by regulatory T (Treg) cells, whose differentiation and function are controlled by the X-chromosome-encoded transcription factor Foxp3 (reviewed in ref.

A Distinct Function of Regulatory T Cells in Tissue Protection.

Regulatory T (Treg) cells suppress immune responses to a broad range of non-microbial and microbial antigens and indirectly limit immune inflammation-inflicted tissue damage by employing multiple mechanisms of suppression. Here, we demonstrate that selective Treg cell deficiency in amphiregulin leads to severe acute lung damage and decreased blood oxygen concentration during influenza virus infection without any measureable alterations in Treg cell suppressor function, antiviral immune responses, or viral load. This tissue repair modality is mobilized in Treg cells in response to inflammatory mediator IL-18 or alarmin IL-33, but not by TCR signaling that is required for suppressor function.

The Cell-Intrinsic Circadian Clock Is Dispensable for Lymphocyte Differentiation and Function.

Circadian rhythms regulate many aspects of physiology, ranging from sleep-wake cycles and metabolic parameters to susceptibility to infection. The molecular clock, with transcription factor BMAL1 at its core, controls both central and cell-intrinsic circadian rhythms. Using a circadian reporter, we observed dynamic regulation of clock activity in lymphocytes.

Regulatory T cell ablation causes acute T cell lymphopenia.

Regulatory T (Treg) cells enforce T cell homeostasis and maintain peripheral T cell tolerance. Here we report a previously unappreciated phenomenon of acute T cell lymphopenia in secondary lymphoid organs and non-lymphoid tissues triggered by Treg cell depletion that precedes the expansion of self-reactive T cells. Lymphopenia affects both neonates and adults indicating a dominant role of Treg cells in maintaining peripheral T cell numbers regardless of the developmental stage.

TGF-β signalling is required for CD4⁺ T cell homeostasis but dispensable for regulatory T cell function.

TGF-β is widely held to be critical for the maintenance and function of regulatory T (T(reg)) cells and thus peripheral tolerance. This is highlighted by constitutive ablation of TGF-β receptor (TR) during thymic development in mice, which leads to a lethal autoimmune syndrome. Here we describe that TGF-β-driven peripheral tolerance is not regulated by TGF-β signalling on mature CD4⁺ T cells.

Dendritic epidermal T cells regulate skin antimicrobial barrier function.

The epidermis, the outer layer of the skin, forms a physical and antimicrobial shield to protect the body from environmental threats. Skin injury severely compromises the epidermal barrier and requires immediate repair. Dendritic epidermal T cells (DETC) reside in the murine epidermis where they sense skin injury and serve as regulators and orchestrators of immune responses.

IL-2-dependent tuning of NK cell sensitivity for target cells is controlled by regulatory T cells.

The emergence of the adaptive immune system took a toll in the form of pathologies mediated by self-reactive cells. Regulatory T cells (T reg cells) exert a critical brake on responses of T and B lymphocytes to self- and foreign antigens. Here, we asked whether T reg cells are required to restrain NK cells, the third lymphocyte lineage, whose features combine innate and adaptive immune cell properties.

IL-2-dependent adaptive control of NK cell homeostasis.

Activation and expansion of T and B lymphocytes and myeloid cells are controlled by Foxp3(+) regulatory T cells (T reg cells), and their deficiency results in a fatal lympho- and myeloproliferative syndrome. A role for T reg cells in the homeostasis of innate lymphocyte lineages remained unknown. Here, we report that T reg cells restrained the expansion of immature CD127(+) NK cells, which had the unique ability to up-regulate the IL2Rα (CD25) in response to the proinflammatory cytokine IL-12.

TCR signaling via Tec kinase ITK and interferon regulatory factor 4 (IRF4) regulates CD8+ T-cell differentiation.

CD8(+) T-cell development in the thymus generates a predominant population of conventional naive cells, along with minor populations of "innate" T cells that resemble memory cells. Recent studies analyzing a variety of KO or knock-in mice have indicated that impairments in the T-cell receptor (TCR) signaling pathway produce increased numbers of innate CD8(+) T cells, characterized by their high expression of CD44, CD122, CXCR3, and the transcription factor, Eomesodermin (Eomes). One component of this altered development is a non-CD8(+) T cell-intrinsic role for IL-4.

PAD4 is not essential for disease in the K/BxN murine autoantibody-mediated model of arthritis.

Introduction: Both murine and human genome-wide association studies have implicated peptidyl arginine deiminase (PAD4) as a susceptibility gene in rheumatoid arthritis (RA). In addition, patients with RA commonly have autoantibodies which recognize PAD4 or and/or citrullinated peptides. This study aims to evaluate the role of PAD4 in the effector phase of arthritis.

PAD4-mediated neutrophil extracellular trap formation is not required for immunity against influenza infection.

During an inflammatory response, neutrophils migrate to the site of infection where they can kill invading pathogens by phagocytosis, secretion of anti-microbicidal mediators or the release of neutrophil extracellular traps (NETs). NETs are specialized anti-microbial structures comprised of decondensed chromatin decorated with microbicidal agents. Increased amount of NETs have been found in patients suffering from the chronic lung inflammatory disease cystic fibrosis, correlating with increased severity of pulmonary obstruction.

Mast cell function is not altered by Coronin-1A deficiency.

Coronin-1A is a WD repeat protein family member, highly expressed in all hematopoietic lineages, and acts as a regulator of F-actin dynamics and Ca2+ signaling. In Coro1a(Lmb3) mice results in inactivation of the protein and leads to disease resistance in a model of lupus erythematosus. In Coro1a(-/-) and Coro1a(Lmb3) mice, peripheral T cells exhibit impairments in survival, migration, activation, and Ca2+ flux.

Effects of a novel arginine methyltransferase inhibitor on T-helper cell cytokine production.

The protein arginine methyltransferase (PRMT) family of enzymes catalyzes the transfer of methyl groups from S-adenosylmethionine to the guanidino nitrogen atom of peptidylarginine to form monomethylarginine or dimethylarginine. We created several less polar analogs of the specific PRMT inhibitor arginine methylation inhibitor-1, and one such compound was found to have improved PRMT inhibitory activity over the parent molecule. The newly identified PRMT inhibitor modulated T-helper-cell function and thus may serve as a lead for further inhibitors useful for the treatment of immune-mediated disease.