Ligand-independent function of ß2-adrenergic receptor affects IgE-mediated Ca2+ influx in mast cells.

BACKGROUND: Mast cells are key effector cells that elicit immunoglobulin E (IgE)-mediated allergic inflammations. Allergen cross-linking of IgE bound to the high-affinity IgE receptor, FcεRI, on mast cells triggers signaling cascades that activate signal proteins and evoke extracellular Ca2+ influx, which are crucial for cytokine production. The ß2-adrenergic receptor (Adrb2) on mast cells negatively regulates FcεRI signaling, as demonstrated by the inhibition of IgE/antigen (Ag)-induced activation by Adrb2 agonists. OBJECTIVE: Although ß2-adrenergic-related reagents are known to influence mast cell functions, the specific intrinsic role of Adrb2 in these cells is not fully understood, potentially because of off-target effects. In this study, the additional roles of Adrb2 in mast cells were investigated, specifically the involvement of Adrb2 in FcεRI signaling, using Adrb2-/- mice. METHODS: Adrb2-/- mice were used to investigate the roles of Adrb2 in mast cells by examining bone marrow-derived mast cells (BMMCs) for surface expression of mast cell markers, granule numbers, and gene expression of mast cell proteases. Cytokine production, Ca2+ influx, and nuclear factor of activated T cells (NFAT) nuclear translocation were measured in Adrb2-/- and Adrb2+/+ BMMCs upon IgE/Ag stimulation. RESULTS: Adrb2-/- did not affect the generation of BMMCs, their surface expression of mast cell markers, granule numbers, or gene expression of mast cell proteases, indicating that the absence of Adrb2 had no adverse effect on mast cell development. However, Adrb2-/- BMMCs exhibited reduced tumor necrosis factor α (TNFα) production and diminished Ca2⁺ influx upon IgE/Ag stimulation, which correlated with decreased NFAT translocation. Restoration of Adrb2 in Adrb2-/- BMMCs rescued cytokine production. Notably, FcεRI-mediated phosphorylation of the phospholipase PLCγ1 and mitogen-activated protein kinases (MAPKs) remained unchanged in the absence of Adrb2. CONCLUSION: These results suggest that Adrb2 has a novel ligand-independent function, increasing Ca2+ entry in mast cells when stimulated with IgE/Ag.

Pretreatment circulating MAIT cells, neutrophils, and periostin predicted the real-world response after 1-year mepolizumab treatment in asthmatics.

BACKGROUND: Mepolizumab treatment improves symptom control and quality of life and reduces exacerbations in patients with severe eosinophilic asthma. However, biomarkers that predict therapeutic effectiveness must be determined for use in precision medicine. Herein, we elucidated the dynamics of various parameters before and after treatment as well as patient characteristics predictive of clinical responsiveness to mepolizumab after 1-year treatment. METHODS: Twenty-seven patients with severe asthma were treated with mepolizumab for one year. Asthma control test scores, pulmonary function tests, fractional exhaled nitric oxide levels, and blood samples were evaluated. Additionally, we explored the role of CD69-positive mucosal-associated invariant T (MAIT) cells as a candidate biomarker for predicting treatment effectiveness by evaluating an OVA-induced asthma murine model using MR1 knockout mice, where MAIT cells were absent. RESULTS: The frequencies of CD69-positive group 1 innate lymphoid cells, group 3 innate lymphoid cells, natural killer cells, and MAIT cells decreased after mepolizumab treatment. The frequency of CD69-positive MAIT cells and neutrophils was lower and serum periostin levels were higher in responders than in non-responders. In the OVA-induced asthma murine model, CD69-positive MAIT cell count in the whole mouse lung was significantly higher than that in the control mice. Moreover, OVA-induced eosinophilic airway inflammation was exacerbated in the MAIT cell-deficient MR1 knockout mice. CONCLUSIONS: This study shows that circulating CD69-positive MAIT cells, neutrophils, and serum periostin might predict the real-world response after 1-year mepolizumab treatment. Furthermore, MAIT cells potentially have a protective role against type 2 airway inflammation.

IL-18 receptor-α signalling pathway contributes to autoantibody-induced arthritis via neutrophil recruitment and mast cell activation.

OBJECTIVES: The interleukin (IL)-18 signalling pathway is involved in animal models of collagen-induced arthritis, but the role of this pathway in autoantibody-induced arthritis is poorly understood. An autoantibody-induced arthritis model, K/BxN serum transfer arthritis, reflects the effector phase of arthritis and is important in innate immunity including neutrophils and mast cells. This study aimed to investigate the role of the IL-18 signalling pathway in autoantibody-induced arthritis using IL-18 receptor (IL-18R) α-deficient mice. METHODS: K/BxN serum transfer arthritis was induced in IL-18Rα-/- and wild-type B6 (controls) mice. The severity of arthritis was graded, and histological and immunohistochemical examinations were performed on paraffin-embedded ankle sections. Total Ribonucleic acid (RNA) isolated from mouse ankle joints was analysed by real-time reverse transcriptase-polymerase chain reaction. RESULTS: IL-18 Rα-/- mice had significantly lower arthritis clinical scores, neutrophil infiltration, and numbers of activated, degranulated mast cells in the arthritic synovium than in controls. IL-1ß, which is indispensable for the progression of arthritis, was significantly downregulated in inflamed ankle tissue in IL-18 Rα-/- mice. CONCLUSIONS: IL-18/IL-18Rα signalling contributes to the development of autoantibody-induced arthritis by enhancing synovial tissue expression of IL-1ß and inducing neutrophil recruitment and mast cell activation. Therefore, inhibition of the IL-18Rα signalling pathway might be a new therapeutic strategy for rheumatoid arthritis.

Harnessing autoimmunity with dominant self-peptide: Modulating the sustainability of tissue-preferential antigen-specific Tregs by governing the binding stability via peptide flanking residues.

Sensitization to self-peptides induces various immunological responses, from autoimmunity to tumor immunity, depending on the peptide sequence; however, the underlying mechanisms remain unclear, and thus, curative therapeutic options considering immunity balance are limited. Herein, two overlapping dominant peptides of myelin proteolipid protein, PLP136-150 and PLP139-151, which induce different forms of experimental autoimmune encephalomyelitis (EAE), monophasic and relapsing EAE, respectively, were investigated. Mice with monophasic EAE exhibited highly resistant to EAE re-induction with any encephalitogenic peptides, whereas mice with relapsing EAE were susceptible, and progressed, to EAE re-induction. This resistance to relapse and re-induction in monophasic EAE mice was associated with the maintenance of potent CD69+CD103+CD4+CD25high regulatory T-cells (Tregs) enriched with antigen specificity, which expanded preferentially in the central nervous system with sustained suppressive activity. This tissue-preferential sustainability of potent antigen-specific Tregs was correlated with the antigenicity of PLP136-150, depending on its flanking residues. That is, the flanking residues of PLP136-150 enable to form pivotally arranged strong hydrogen bonds that secured its binding stability to MHC-class II. These potent Tregs acting tissue-preferentially were induced only by sensitization of PLP136-150, not by its tolerance induction, independent of EAE development. These findings suggest that, for optimal therapy, "benign autoimmunity" can be critically achieved through inverse vaccination with self-peptides by manipulating their flanking residues.

Alterations of the gut ecological and functional microenvironment in different stages of multiple sclerosis.

Multiple sclerosis (MS), an autoimmune disease of the central nervous system, generally starts as the relapsing remitting form (RRMS), but often shifts into secondary progressive MS (SPMS). SPMS represents a more advanced stage of MS, characterized by accumulating disabilities and refractoriness to medications. The aim of this study was to clarify the microbial and functional differences in gut microbiomes of the different stages of MS. Here, we compared gut microbiomes of patients with RRMS, SPMS, and two closely related disorders with healthy controls (HCs) by 16S rRNA gene and whole metagenomic sequencing data from fecal samples and by fecal metabolites. Each patient group had a number of species having significant changes in abundance in comparison with HCs, including short-chain fatty acid (SCFA)-producing bacteria reduced in MS. Changes in some species had close association with clinical severity of the patients. A marked reduction in butyrate and propionate biosynthesis and corresponding metabolic changes were confirmed in RRMS compared with HCs. Although bacterial composition analysis showed limited differences between the patient groups, metagenomic functional data disclosed an increase in microbial genes involved in DNA mismatch repair in SPMS as compared to RRMS. Together with an increased ratio of cysteine persulfide to cysteine in SPMS revealed by sulfur metabolomics, we postulate that excessive DNA oxidation could take place in the gut of SPMS. Thus, gut ecological and functional microenvironments were significantly altered in the different stages of MS. In particular, reduced SCFA biosynthesis in RRMS and elevated oxidative level in SPMS were characteristic.

Gut dysbiosis and multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) and T cell-mediated autoimmune processes are assumed to be involved in its pathogenesis. Recently, accumulating evidence has indicated that commensal bacteria interact with the host immune system and that the alteration of commensal bacteria composition, termed dysbiosis, is associated with various autoimmune diseases including CNS autoimmune diseases. In this review, we introduce recent findings regarding the association between gut microbiota and MS and related diseases and microbiota function in an animal model of MS.

Dysregulated B cell differentiation towards antibody-secreting cells in neuromyelitis optica spectrum disorder.

BACKGROUND: Anti-aquaporin 4 (AQP4) antibody (AQP4-Ab) is involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD). However, the mechanism involved in AQP4-Ab production remains unclear. METHODS: We analyzed the immunophenotypes of patients with NMOSD and other neuroinflammatory diseases as well as healthy controls (HC) using flow cytometry. Transcriptome analysis of B cell subsets obtained from NMOSD patients and HCs was performed. The differentiation capacity of B cell subsets into antibody-secreting cells was analyzed. RESULTS: The frequencies of switched memory B (SMB) cells and plasmablasts were increased and that of naïve B cells was decreased in NMOSD patients compared with relapsing-remitting multiple sclerosis patients and HC. SMB cells from NMOSD patients had an enhanced potential to differentiate into antibody-secreting cells when cocultured with T peripheral helper cells. Transcriptome analysis revealed that the profiles of B cell lineage transcription factors in NMOSD were skewed towards antibody-secreting cells and that IL-2 signaling was upregulated, particularly in naïve B cells. Naïve B cells expressing CD25, a receptor of IL-2, were increased in NMOSD patients and had a higher potential to differentiate into antibody-secreting cells, suggesting CD25+ naïve B cells are committed to differentiate into antibody-secreting cells. CONCLUSIONS: To the best of our knowledge, this is the first study to demonstrate that B cells in NMOSD patients are abnormally skewed towards antibody-secreting cells at the transcriptome level during the early differentiation phase, and that IL-2 might participate in this pathogenic process. Our study indicates that CD25+ naïve B cells are a novel candidate precursor of antibody-secreting cells in autoimmune diseases.

Characteristics of mucosal-associated invariant T cells and their roles in immune diseases.

Mucosal-associated invariant T (MAIT) cells are a subset of innate-like T cells that express a semi-invariant T-cell receptor and are restricted by the major histocompatibility complex class I-related molecule 1 (MR1). MAIT cells recognize biosynthetic derivatives of the riboflavin synthesis pathway present in microbes. MAIT cells have attracted increased interest related to various immune responses because of their unique features including their abundance in humans, non-peptidic antigens and ability to respond to antigenic and non-antigenic stimuli. The numbers of circulating MAIT cells are decreased in many immune diseases such as multiple sclerosis, systemic lupus erythematosus and inflammatory bowel diseases. However, the remaining MAIT cells have an increased cytokine-producing capacity and activated status, which are related to disease activity. Additionally, MAIT cells have been observed at sites of inflammation including the kidneys, synovial fluid and intestinal mucosa. These findings suggest their involvement in the pathogenesis of immune diseases. In this mini-review, we summarize the recent findings of MAIT cells in human immune diseases and animal models, and discuss their role and potential as a therapeutic target.

The importance of specific citrullinated clusterin and vimentin found in a multi-coloured bead-based citrulline-peptide array system in rheumatoid arthritis.

OBJECTIVES: The importance of citrullination in rheumatoid arthritis (RA) has been reported, but the degree to which individual citrullinated proteins affect the onset and progression of RA is still unclear. We aimed to identify citrullinated proteins that may play an important role in the onset and progression of RA using an individualised anti-citrullinated protein antibody (ACPA) evaluation system with citrullinated peptides as probes. METHODS: Serum samples from 50 normal donors and 51 RA patients were evaluated using a custom MagPlexTM bead array with 13 types of citrullinated peptide. The presence/absence of ACPAs that react to each citrullinated peptide in each subject was determined using the Z-score, which was calculated based on the fluorescence intensity distribution of a sample from a normal donor. Whether the fluorescence intensity was inhibited when free citrullinated peptides were added to a system was also evaluated. RESULTS: Median fluorescence intensities obtained from beads coupled with the 13 types of citrullinated peptide were all significantly higher in RA patients versus normal donors. With a Z-score ≥2 as the cut-off value for the presence of ACPAs, ACPAs that recognised five types of citrullinated peptides derived from fibrinogen A, fillagrin, clusterin, and vimentin were widely detected in RA patients. In addition, inhibition experiments showed that citrullinated vimentin, clusterin, and enolase 1A peptides inhibited coupling of ACPAs to other citrullinated peptides. CONCLUSIONS: ACPAs to many citrullinated proteins exhibited cross-reactivity to citrullinated clusterin and vimentin, suggesting the importance of citrullinated clusterin and vimentin in the early stages of RA pathogenesis.

Reconstitution of Circulating Mucosal-Associated Invariant T Cells after Allogeneic Hematopoietic Cell Transplantation: Its Association with the Riboflavin Synthetic Pathway of Gut Microbiota in Cord Blood Transplant Recipients.

Mucosal-associated invariant T (MAIT) cells are a type of innate lymphocyte and recognize riboflavin (vitamin B2) synthesis products presented by MHC-related protein 1. We investigated long-term reconstitution of MAIT cells and its association with chronic graft-versus-host disease (cGVHD) in a cross-sectional cohort of 173 adult patients after allogeneic hematopoietic cell transplantation. According to donor source, the number of MAIT cells significantly correlated with time after cord blood transplantation (CBT) but not with time after bone marrow transplantation or peripheral blood stem cell transplantation. The number of MAIT cells was significantly lower in patients with cGVHD compared with patients without cGVHD. We also examined the association between MAIT cell reconstitution and gut microbiota as evaluated by 16S ribosomal sequencing of stool samples 1 mo post-CBT in 27 adult patients undergoing CBT. The diversity of gut microbiota was positively correlated with better MAIT cell reconstitution after CBT. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States analysis indicated that amounts of ribB and ribA genes were significantly higher in the microbiomes of patients with subsequent MAIT cell reconstitution after CBT. In conclusion, long-term MAIT cell reconstitution is dependent on the type of donor source. Our data also unveiled an important role for the interaction of circulating MAIT cells with gut microbiota in humans.

Inhibition of mTOR suppresses IFNα production and the STING pathway in monocytes from systemic lupus erythematosus patients.

OBJECTIVE: Increased IFNα is important in the pathogenesis of SLE. Plasmacytoid dendritic cells are considered the main producer of IFNα upon Toll-like receptor pathway activation. However, which cells produce IFNα following stimulation with cyclic GMP-AMP synthase (cGAS) and stimulator of IFN genes (STING) in SLE remains unknown. We investigated the IFNα producing capacity of myeloid cells under cGAS-STING pathway stimulation. METHODS: IFNα levels in peripheral blood mononuclear cells from SLE patients and healthy controls stimulated with 2'3'c-GAMP, a stimulator of cGAS-STING, were measured by intracellular cytokine staining and flow cytometry. STING expression and its co-localization with TBK1 were examined by flow cytometry or confocal microscopy. The effects of in vitro exposure to IFNα on IFNα production and STING expression, and in vitro rapamycin treatment on IFNα production and STING, pTBK1 and IRF3 expression were examined. RESULTS: IFNα was produced by monocytes, conventional dendritic cells and plasmacytoid dendritic cells upon cGAS-STING pathway activation. The frequency of IFNα-producing monocytes positively correlated with SLE disease activity. STING expression and its co-localization with TBK1 were increased in lupus monocytes. Prior exposure to IFNα enhanced the IFNα-producing capacity of monocytes. Inhibition of the mechanistic target of the rapamycin (mTOR) pathway suppressed IFNα production from monocytes and downregulated enhanced STING expression and its downstream molecules. CONCLUSION: Enhanced IFNα from lupus monocytes induced by augmented STING pathway activation is associated with SLE pathogenesis. Suppression of the mTOR pathway downregulated the enhanced STING expression and the subsequent IFNα production by monocytes.

Association of mucosal-associated invariant T cells with different disease phases of polymyalgia rheumatica.

OBJECTIVES: Although T cells are thought to be involved in the pathogenesis of PMR, whether innate-like T cells are involved in the process remains unknown. METHODS: The serum levels of 27 cytokines/chemokines in patients with PMR were measured by a multiplex immunoassay (Bio-Plex Assay). The cytokine-producing capacity of T and innate-like T cells was assessed by intracellular cytokine staining and flow cytometry. The frequency and activated status of T and innate-like T cells were investigated by flow cytometry and their associations with clinical parameters were assessed. RESULTS: The levels of inflammatory cytokines were associated with disease activity in PMR. The cytokine-producing capacity by CD8+ T and innate-like T cells was associated with disease activity. The frequency of HLA-DR+ CD38+ cells among CD8+ T cells was increased in patients with active disease. The frequencies of HLA-DR+ CD38+ cells among CD4+ T, mucosal-associated invariant T (MAIT) and γδ T cells were higher in patients with inactive disease. The frequency of HLA-DR+ CD38+ MAIT cells was associated with the PMR activity score and CRP levels in patients in remission. CONCLUSION: The inflammatory cytokine-producing capacity and expression of activation markers of CD8+ T and innate-like T cells were associated with the disease activity of PMR. MAIT cell activation in patients in remission may contribute to the subclinical activity of the disease.

Butyrate suppresses demyelination and enhances remyelination.

BACKGROUND: The association of gut microbiota and diseases of the central nervous system (CNS), including multiple sclerosis (MS), has attracted much attention. Although a previous analysis of MS gut microbiota revealed a reduction in species producing short-chain fatty acids (SCFAs), the influence of these metabolites on demyelination and remyelination, the critical factors of MS pathogenesis, remains unclear. METHODS: To investigate the relationship between demyelination and gut microbiota, we administered a mixture of non-absorbing antibiotics or SCFAs to mice with cuprizone-induced demyelination and evaluated demyelination and the accumulation of microglia. To analyze the direct effect of SCFAs on demyelination or remyelination, we induced demyelination in an organotypic cerebellar slice culture using lysolecithin and analyzed the demyelination and maturation of oligodendrocyte precursor cells with or without SCFA treatment. RESULTS: The oral administration of antibiotics significantly enhanced cuprizone-induced demyelination. The oral administration of butyrate significantly ameliorated demyelination, even though the accumulation of microglia into demyelinated lesions was not affected. Furthermore, we showed that butyrate treatment significantly suppressed lysolecithin-induced demyelination and enhanced remyelination in an organotypic slice culture in the presence or absence of microglia, suggesting that butyrate may affect oligodendrocytes directly. Butyrate treatment facilitated the differentiation of immature oligodendrocytes. CONCLUSIONS: We revealed that treatment with butyrate suppressed demyelination and enhanced remyelination in an organotypic slice culture in association with facilitating oligodendrocyte differentiation. Our findings shed light on a novel mechanism of interaction between the metabolites of gut microbiota and the CNS and may provide a strategy to control demyelination and remyelination in MS.

Expanded circulating peripheral helper T cells in systemic lupus erythematosus: association with disease activity and B cell differentiation.

OBJECTIVE: Peripheral helper T (TPH) cells are a recently identified Th cell subset that promotes B cell differentiation and antibody production in inflamed tissues. This study investigated circulating TPH cells to determine their involvement in systemic lupus erythematosus (SLE). METHODS: Peripheral blood mononuclear cells collected from SLE patients and healthy individuals were analysed. TPH cells were identified as CD3+CD4+CD45RA-CXCR5- cells with a high expression of PD-1. The frequency, activation status and subsets of TPH cells were evaluated by flow cytometry. The production of IL-21 was assessed by intracellular staining and the association of TPH cells with disease activity and B cell populations was determined. RESULTS: Circulating TPH cells, identified as CD3+CD4+CD45RA-PD-1highCXCR5- cells were increased in the peripheral blood of SLE patients compared with controls. Circulating TPH cells produced similar amounts of IL-21 compared with follicular Th cells. The expansion and activation of TPH cells were correlated with SLE disease activity. Activated TPH cells, particularly Th1-type TPH cells, were associated with the promotion of B cell differentiation in SLE patients. CONCLUSION: The association of TPH cells with disease activity suggests the involvement of extrafollicular T-B cell interactions in the pathogenesis of SLE. TPH cells promote autoantibody production in aberrant lymphoid organs and therefore might be a novel therapeutic target in autoantibody-producing disorders.

Cutting Edge: Anti-TIM-3 Treatment Exacerbates Pulmonary Inflammation and Fibrosis in Mice.

Promising results of immune checkpoint inhibitors have indicated the use of immunotherapy against malignant tumors. However, they cause serious side effects, including autoimmune diseases and pneumonitis. T cell Ig and mucin domain (TIM)-3 is a new candidate immune checkpoint molecule; however, the potential toxicity associated with anti-TIM-3 treatment is unknown. In this study, we investigated the pathological contribution of anti-TIM-3 mAb in a bleomycin-induced lung inflammation and fibrosis model. Anti-TIM-3-treated mice showed more severe inflammation and peribronchiolar fibrosis compared with control IgG-treated mice. Anti-TIM-3 mAb was associated with increased numbers of myofibroblasts, collagen deposition, and TGF-ß1 production in lungs. TIM-3 expression was only detected on alveolar macrophages that protect against fibrosis by apoptotic cell clearance. Treatment with anti-TIM-3 mAb inhibited the phagocytic ability of alveolar macrophages in vivo, resulting in the defective clearance of apoptotic cells in lungs. In summary, anti-TIM-3 mAb treatment might cause pneumonitis and it should be used with caution in clinical settings.

Maternal High Fiber Diet during Pregnancy and Lactation Influences Regulatory T Cell Differentiation in Offspring in Mice.

Short-chain fatty acids (SCFAs), the end products of dietary fiber, influence the immune system. Moreover, during pregnancy the maternal microbiome has a great impact on the development of the offspring's immune system. However, the exact mechanisms by which maternal SCFAs during pregnancy and lactation influence the immune system of offspring are not fully understood. We investigated the molecular mechanisms underlying regulatory T cell (Treg) differentiation in offspring regulated by a maternal high fiber diet (HFD). Plasma levels of SCFAs in offspring from HFD-fed mice were higher than in those from no fiber diet-fed mice. Consequently, the offspring from HFD-fed mice had higher frequencies of thymic Treg (tTreg) and peripheral Tregs We found that the offspring of HFD-fed mice exhibited higher autoimmune regulator (Aire) expression, a transcription factor expressed in the thymic microenvironment, suggesting SCFAs promote tTreg differentiation through increased Aire expression. Notably, the receptor for butyrate, G protein-coupled receptor 41 (GPR41), is highly expressed in the thymic microenvironment and Aire expression is not increased by stimulation with butyrate in GPR41-deficient mice. Our studies highlight the significance of SCFAs produced by a maternal HFD for Treg differentiation in the thymus of offspring. Given that Aire expression is associated with the induction of tTregs, the maternal microbiome influences Treg differentiation in the thymus of offspring through GPR41-mediated Aire expression.

Breast-feeding regulates immune system development via transforming growth factor-ß in mice pups.

BACKGROUND: Breast milk contains important nutrients and immunoregulatory factors that are essential for newborn infants. Recently, epidemiological studies suggested that breast-feeding prevents a wide range of infectious diseases and lowers the incidence of infant allergic diseases. METHODS: To examine the effects of breast milk on immunological development in infancy, we established an artificial rearing system for hand-feeding mice and compared mouse pups fed with either breast milk or milk substitute. All mice were killed at 14 days of age and immune cells in the thymus, spleen, and small intestine were examined on flow cytometry. RESULTS: The number of thymocytes was higher whereas that of total immune cells of peripheral lymphoid tissues was lower in mice fed breast milk compared with milk substitute-fed mice. In peripheral lymphoid tissues, the proportion of B cells was higher and that of CD8+ T cells, macrophages, dendritic cells, and granulocytes was significantly lower in breast milk-fed mice. The same alteration in immune cells of the thymus and peripheral lymphoid tissues in milk substitute-fed mice was also observed in pups reared by mother mice treated with anti-transforming growth factor-ß (anti-TGF-ß) monoclonal antibody. CONCLUSIONS: Breast milk regulates the differentiation and expansion of innate and adaptive immune cells partly due to TGF-ß. Hence, TGF-ß in breast milk may be a new therapeutic target for innate immune system-mediated diseases of infancy.

MicroRNA-101a regulates microglial morphology and inflammation.

BACKGROUND: Microglia, as well as other tissue-resident macrophages, arise from yolk sac progenitors. Thus, it is likely that the central nervous system environment is critical for the acquisition of a distinct microglial phenotype. Several microRNAs that are enriched in the brain play crucial roles in brain development and may also play a role in the differentiation of microglia. METHODS: To track the differentiation of hematopoietic cells into microglia, lineage-negative bone marrow cells were co-cultured with astrocytes in the absence or presence of microRNAs or their inhibitors. Microglia-like cells were identified as small, round cells that were immunopositive for CD11b, Iba1, CX3CR1, and triggering receptor expressed on myeloid cells (TREM)-2. RESULTS: Five microRNAs (miR-101a, miR-139-3p, miR-214*, miR-218, and miR-1186) were identified as modifiers of the differentiation of bone marrow-derived microglia-like cells. Among them, miR-101a facilitated the differentiation of bone marrow cells into microglia-like cells most potently. Small, round cells expressing CD11b, Iba1, CX3CR1, and TREM-2 were predominant in cells treated by miR-101a. miR-101a was abundantly expressed in non-microglial brain cells. Transfection of miR-101a into microglia significantly increased the production of IL-6 in response to LPS. Finally, miR-101a downregulated the expression of MAPK phosphatase-1. CONCLUSIONS: miR-101a, which is enriched in the brain, promotes the differentiation of bone marrow cells into microglia-like cells.

Circulating activated innate lymphoid cells and mucosal-associated invariant T cells are associated with airflow limitation in patients with asthma.

BACKGROUND: A variety of innate subsets of lymphoid cells such as natural killer (NK) cells, several populations of innate lymphoid cells (ILCs), and mucosal-associated invariant T (MAIT) cells as innate-like T lymphocytes are involved in asthma and may have important effector functions in asthmatic immune responses. In the present study, we investigated whether NK cells, ILCs, and MAIT cells in the peripheral blood of patients with asthma would be associated with clinical asthma parameters. METHODS: We recruited 75 adult patients with mild to severe asthma. The peripheral blood mononuclear cells in peripheral venous blood samples from the patients were purified and stained with different combinations of appropriate antibodies. The cells were analyzed by flow cytometry. RESULTS: The percentage of activated (i.e., CD69+) NK cells in the total NK cell population was negatively correlated with FEV1% which is calculated by the forced expiratory volume in 1 s (FEV1)/the forced vital capacity (FVC). The percentages of CD69+ ILC1s and ILC2s were negatively correlated with FEV1% and %FEV1. The percentage of CD69+ ILC3s was positively correlated with BMI, and the percentage of CD69+ MAIT cells was negatively correlated with FEV1%. Moreover, the percentage of CD69+ NK cells, ILC1s, ILC2s, ILC3s, and MAIT cells were positively correlated with each other. CONCLUSIONS: For the first time, our data showed that activated NK cells, ILC1s, ILC2s, ILC3s, and MAIT cells were positively correlated with each other and may be associated with airflow limitation in patients with asthma.

MAIT cells are activated and accumulated in the inflamed mucosa of ulcerative colitis.

BACKGROUND AND AIM: Ulcerative colitis (UC) is a chronic, relapsing and remitting, inflammatory disorder of the large intestine. Mucosal associated invariant T (MAIT) cells are a member of innate-like lymphocytes found abundantly in the mucosal tissue. The contribution of MAIT cells in the pathogenesis of UC is still unclear; therefore, this study aimed at investigating the role of these cells in patients with UC. METHODS: The frequency of MAIT cells, as well as the production of cytokines and expression levels of activation markers by these cells in the peripheral blood of UC patients and healthy controls, was analyzed by flow cytometry. MAIT cells were also quantified in colon biopsies of UC patients using a confocal microscope. RESULTS: There was a significant reduction in MAIT cell frequency in the peripheral blood of UC patients compared with healthy controls (P < 0.0001). MAIT cells from UC patients secreted more interleukin (IL)-17 than healthy controls (P < 0.05). The expression levels of CD69 on these cells were correlated with disease activity and endoscopic scores and plasma levels of IL-18. Furthermore, MAIT cells increased in the inflamed mucosa, and their frequency was correlated with clinical and endoscopic disease activity in UC patients. CONCLUSIONS: The findings from this study indicate that MAIT cells could be associated with UC and may serve as potential biomarkers or therapeutic targets in UC.