An early regulatory mechanism of hyperinflammation by restricting monocyte contribution.

Innate immune cells play a key role in inflammation as a source of pro-inflammatory cytokines. However, it remains unclear how innate immunity-mediated inflammation is fine-tuned to minimize tissue damage and assure the host's survival at the early phase of systemic inflammation. The results of this study with mouse models demonstrate that the supply of monocytes is restricted depending on the magnitude of inflammation.

IL-27 regulates the differentiation of follicular helper NKT cells via metabolic adaptation of mitochondria.

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that express an invariant T cell receptor α chain and contribute to bridging innate and acquired immunity with rapid production of large amounts of cytokines after stimulation. Among effecter subsets of iNKT cells, follicular helper NKT (NKT) cells are specialized to help B cells. However, the mechanisms of NKT cell differentiation remain to be elucidated.

Notch2 with retinoic acid license IL-23 expression by intestinal EpCAM+ DCIR2+ cDC2s in mice.

Despite the importance of IL-23 in mucosal host defense and disease pathogenesis, the mechanisms regulating the development of IL-23-producing mononuclear phagocytes remain poorly understood. Here, we employed an Il23aVenus reporter strain to investigate the developmental identity and functional regulation of IL-23-producing cells. We showed that flagellin stimulation or Citrobacter rodentium infection led to robust induction of IL-23-producing EpCAM+ DCIR2+ CD103- cDC2s, termed cDCIL23, which was confined to gut-associated lymphoid tissues, including the mesenteric lymph nodes, cryptopatches, and isolated lymphoid follicles.

Hematopoietic cell-derived IL-15 supports NK cell development in scattered and clustered localization within the bone marrow.

Natural killer (NK) cells are innate immune cells critical for protective immune responses against infection and cancer. Although NK cells differentiate in the bone marrow (BM) in an interleukin-15 (IL-15)-dependent manner, the cellular source of IL-15 remains elusive. Using NK cell reporter mice, we show that NK cells are localized in the BM in scattered and clustered manners.

Myeloid-like B cells boost emergency myelopoiesis through IL-10 production during infection.

Emergency myelopoiesis (EM) is a hematopoietic response against systemic infections that quickly supplies innate immune cells. As lymphopoiesis is strongly suppressed during EM, the role of lymphocytes in that process has not received much attention. Here, we found that myeloid-like B cells (M-B cells), which express myeloid markers, emerge in the bone marrow (BM) after the induction of EM.

A circulating subset of iNKT cells mediates antitumor and antiviral immunity.

Invariant natural killer T (iNKT) cells are a group of innate-like T lymphocytes that recognize lipid antigens. They are supposed to be tissue resident and important for systemic and local immune regulation. To investigate the heterogeneity of iNKT cells, we recharacterized iNKT cells in the thymus and peripheral tissues.

Commitment to dendritic cells and monocytes.

Dendritic cells (DCs) and monocytes are widely conserved immune cells in vertebrates that arise from hematopoietic stem cells via intermediate progenitors. The progenitors that strictly give rise to DCs or monocytes have been recently identified both in humans and in mice, thereby revealing their differentiation pathways. Advances in analysis technologies have further deepened our understanding of the development of DCs and monocytes from progenitor population-based to individual progenitor cell-based commitment.

Prolonged high-intensity exercise induces fluctuating immune responses to herpes simplex virus infection via glucocorticoids.

Background: Epidemiologic studies have yielded conflicting results regarding the influence of a single bout of prolonged high-intensity exercise on viral infection.

Objective: We sought to learn whether prolonged high-intensity exercise either exacerbates or ameliorates herpes simplex virus type 2 (HSV-2) infection according to the interval between virus exposure and exercise.

Methods: Mice were intravaginally infected with HSV-2 and exposed to run on the treadmill.

IRF2 maintains the stemness of colonic stem cells by limiting physiological stress from interferon.

The physiological stresses that diminish tissue stem-cell characteristics remain largely unknown. We previously reported that type I interferon (IFN), which is essential for host antiviral responses, is a physiological stressor for hematopoietic stem cells (HSCs) and small intestinal stem cells (ISCs) and that interferon regulatory factor-2 (IRF2), which attenuates IFN signaling, maintains their stemness. Here, using a dextran sodium sulfate (DSS)-induced colitis model, we explore the role of IRF2 in maintaining colonic epithelial stem cells (CoSCs).

Autophagy Detection in Intestinal Stem Cells.

Autophagy is a lysosomal degradation pathway with important roles in physiological homeostasis and disease. We previously showed that intrinsic autophagy in intestinal stem cells (ISCs) is important for ISC homeostasis. Here we describe the detailed methods for detecting autophagy in ISCs by observing autophagosomes in GFP-LC3 transgenic mice and quantifying the p62 protein levels.

Regulated IFN signalling preserves the stemness of intestinal stem cells by restricting differentiation into secretory-cell lineages.

Intestinal stem cells (ISCs) are located at the crypt base and fine-tune the balance of their self-renewal and differentiation, but the physiological mechanism involved in regulating that balance remains unknown. Here we describe a transcriptional regulator that preserves the stemness of ISCs by restricting their differentiation into secretory-cell lineages. Interferon regulatory factor 2 (IRF2) negatively regulates interferon signalling, and mice completely lacking Irf2 or with a selective Irf2 deletion in their intestinal epithelial cells have significantly fewer crypt Lgr5 ISCs than control mice.

Characterization of radioresistant epithelial stem cell heterogeneity in the damaged mouse intestine.

The small intestine has a robust regenerative capacity, and various cell types serve as "cells-of-origin" in the epithelial regeneration process after injury. However, how much each population contributes to regeneration remains unclear. Using lineage tracing, we found that Lgr5-expressing cell derivatives contained radioresistant intestinal stem cells (ISCs) crucial for epithelial regeneration in the damaged intestine after irradiation.

CD86-based analysis enables observation of bona fide hematopoietic responses.

Hematopoiesis is a system that provides red blood cells (RBCs), leukocytes, and platelets, which are essential for oxygen transport, biodefense, and hemostasis; its balance thus affects the outcome of various disorders. Here, we report that stem cell antigen-1 (Sca-1), a cell surface marker commonly used for the identification of multipotent hematopoietic progenitors (Lin-Sca-1+c-Kit+ cells; LSKs), is not suitable for the analysis of hematopoietic responses under biological stresses with interferon production. Lin-Sca-1-c-Kit+ cells (LKs), downstream progenitors of LSKs, acquire Sca-1 expression upon inflammation, which makes it impossible to distinguish between LSKs and LKs.

Propolis induces Ca signaling in immune cells.

Propolis possesses several immunological functions. We recently generated a conditional Ca biosensor yellow cameleon (YC3.60) transgenic mouse line and established a five-dimensional (5D) (x, y, z, time, and Ca signaling) system for intravital imaging of lymphoid tissues, including Peyer's patches (PPs).

Role of eosinophils in a murine model of inflammatory bowel disease.

Ulcerative colitis (UC) is a form of inflammatory bowel disease (IBD), which is triggered spontaneously by unknown mechanisms and manifests as chronic and relapsing inflammatory conditions in the colon. Eosinophil infiltration is often observed in the colonic tissue of ulcerative colitis patients. However, the role of eosinophils in the disease has not been well defined.

Monopoiesis in humans and mice.

Monocytes are a widely conserved cell population in vertebrates with important roles in both inflammation and homeostasis. Under both settings, monocytes continuously arise from hematopoietic progenitors in the bone marrow and, on demand, migrate into tissues through the bloodstream. Monocytes are classified into three subsets-classical, intermediate and non-classical-based on their cell surface expression of CD14 and CD16 in humans and Ly6C, CX3CR1 and CCR2 in mice.

[Identification of a human progenitor strictly committed to monocytic differentiation: a counterpart of mouse cMoPs].

Monocytes give rise to macrophages and dendritic cells (DCs) under steady-state and inflammatory conditions, thereby contributing to host defense and tissue pathology. Inflammation triggers the differentiation of tissue-infiltrating monocytes into monocyte-derived macrophages and DCs, which are associated with homeostatic host defense reactions and inflammatory diseases. In mice, monocytes are divided into classical Ly6c- and non-classical Ly6c-expressing subsets.

IFN-γ-dependent epigenetic regulation instructs colitogenic monocyte/macrophage lineage differentiation in vivo.

Colonic macrophages induce pathogenic inflammation against commensal bacteria, leading to inflammatory bowel disease (IBD). Although the ontogeny of colonic macrophages has been well studied in the past decade, how macrophages gain colitogenic properties during the development of colitis is unknown. Using a chemically induced colitis model, we showed that accumulated Ly6C cells consisting of inflammatory monocytes and inflammatory macrophages strongly expressed representative colitogenic mediators such as tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS).

Flexible fate commitment of E2-2high common DC progenitors implies tuning in tissue microenvironments.

The basic helix-loop-helix transcription factor E2-2 is essential for the development of plasmacytoid dendritic cells (pDCs) but not conventional DCs (cDCs). Here, we generated E2-2 reporter mice and demonstrated that an E2-2high fraction among common DC progenitors, which are a major source of pDCs and cDCs in the steady state, strictly gave rise to pDCs in the presence of Flt3 (Fms-like tyrosine kinase receptor-3) ligand ex vivo or in the secondary lymphoid organs when transferred in vivo. However, in the small intestine, some of these E2-2high progenitors differentiated into cDCs that produced retinoic acid.

Mast cell hyperactivity underpins the development of oxygen-induced retinopathy.

Mast cells are classically thought to play an important role in protection against helminth infections and in the induction of allergic diseases; however, recent studies indicate that these cells also contribute to neovascularization, which is critical for tissue remodeling, chronic inflammation, and carcinogenesis. Here, we demonstrate that mast cells are essential for sprouting angiogenesis in a murine model of oxygen-induced retinopathy (OIR). Although mouse strains lacking mast cells did not exhibit retinal neovascularization following hypoxia, these mice developed OIR following infusion of mast cells or after injection of mast cell tryptase (MCT).