Eosinophils Contribute to Oral Tolerance via Induction of RORγt-Positive Antigen-Presenting Cells and RORγt-Positive Regulatory T Cells.

Oral tolerance has been defined as the specific suppression of immune responses to an antigen by prior oral administration of the antigen. It has been thought to serve to suppress food allergy. Previous studies have shown that dendritic cells (DCs) and regulatory T cells (Tregs) are involved in the induction of oral tolerance. However, the detailed mechanisms of Treg induction in oral tolerance remain largely unknown. Eosinophils have been recognized as effector cells in allergic diseases, but in recent years, the diverse functions of tissue-resident eosinophils have been reported. Eosinophils in the intestine have been reported to induce Tregs by releasing TGF-ß, but the role of eosinophils in oral tolerance is still controversial. In this study, we analyzed the roles of eosinophils in oral tolerance using eosinophil-deficient ΔdblGATA mice (mice lacking a high-affinity GATA-binding site in the GATA1 promoter). ΔdblGATA mice showed impaired antigen-induced oral tolerance compared to wild-type mice. The induction of RORγt+ Tregs in mesenteric lymph nodes (MLNs) by oral tolerance induction was impaired in ΔdblGATA mice compared to wild-type mice. An increase in RORγt+ antigen-presenting cells (APCs), which are involved in RORγt+ Treg differentiation, in the intestine and MLNs was not seen in ΔdblGATA mice. Notably, the expansion of group 3 innate lymphoid cells (ILC3s), a subset of RORγt+ APCs, by oral tolerance induction was seen in wild-type mice but not ΔdblGATA mice. These results suggest that eosinophils are crucial in the induction of oral tolerance, possibly via the induction of RORγt+ APCs and RORγt+ Tregs.

CCR4 predicts the efficacy of abatacept in rheumatoid arthritis patients through the estimation of Th17 and Treg cell abundance.

OBJECTIVE: Predicting the efficacy of biological disease-modifying anti-rhematic drugs (bDMARDs) is challenging. In this study, we aimed to explore markers that predict the efficacy of abatacept in rheumatoid arthritis (RA) patients. METHODS: Thirty RA patients receiving abatacept were recruited, and peripheral blood mononuclear cells (PBMCs) from the participants were subjected to DNA microarray analysis. The expression of CCR4, which was selected by the result of DNA microarray, was determined by flow cytometry in 16 newly diagnosed treatment-naïve RA patients. CCR4 expression on each helper T cell subset was also measured. RESULTS: CCR4 was upregulated in the abatacept responder. The expression levels of CCR4 were significantly correlated with the improvement of clinical disease activity index (CDAI). CCR4 expression was predominantly observed in CD4+ T cells in PBMCs. The percentage of CCR4-expressing CD4+ T cells was significantly higher in RA patients than in healthy individuals. Interestingly, Th17 and Treg cells expressed high levels of CCR4 compared to non-Th17-related helper T cells. CONCLUSION: CCR4 is a Th17- and Treg-related gene, and the high CCR4 expression in peripheral blood samples may predict the efficacy of abatacept in RA.

A role of Achaete-scute complex homolog 2 in T follicular regulatory cell development.

T follicular regulatory (Tfr) cells, a subset of CD4+ Foxp3+ regulatory T (Treg) cells, locate to the lymphoid follicle and germinal center (GC) and regulate antibody responses. Tfr cells express the functional molecules of follicular helper T (Tfh) cells, including CXCR5 and Bcl6. CD25- mature Tfr cells differentiate from CD25+ Treg cells through CD25+ immature Tfr cells. Others and we have shown that Achaete-scute complex homolog 2 (Ascl2) plays a role in Tfh cell development; however, the role of Ascl2 in the development of Tfr cells remains unclear. Here, we found that Ascl2 was highly and preferentially expressed in CD25+ Tfr cells and CD25- Tfr cells, and that the differentiation from CD25+ Tfr cells to CD25- Tfr cells was impaired by the absence of Ascl2. Furthermore, the forced Ascl2 expression in Treg cells downregulated CD25 expression and suppressed IL-2-induced phosphorylation of STAT5, which is known to suppress CD25- Tfr cell development. Finally, we found that the downregulation of CD25 by Ascl2 in Treg cells is independent of Bach2, which also regulates CD25 downregulation in CD25+ Tfr cells. These results suggest that Ascl2 plays a vital role in developing Tfr cells, possibly by downregulating CD25 expression in a Bach2-independent mechanism.

A20 (Tnfaip3) expressed in CD4+ T cells suppresses Th2 cell-mediated allergic airway inflammation in mice.

A20 (Tnfaip3), a ubiquitin-editing enzyme, inhibits NF-κB signaling pathways in response to pro-inflammatory cytokines. Previous studies have proved the anti-inflammatory roles of A20 in various cell types, including T cells, B cells, dendritic cells, and intestinal epithelial cells. Moreover, recent studies have shown that A20 expressed in lung epithelial cells is required for LPS-induced protection from asthma. In humans, a single-nucleotide polymorphism in TNFAIP3 is associated with asthma risk. However, the role of A20 expressed in T cells in asthmatic responses has not been elucidated. We addressed this point by generating mice lacking A20 expression in T cells (CD4-CreA20 fl/fl mice). We found that house dust mite (HDM)-induced allergic airway inflammation, mucus production, airway hyperresponsiveness, and Th2 cytokine production were significantly exacerbated in CD4-CreA20 fl/fl mice compared with those in control A20 fl/fl mice. In vitro differentiation of Th2 cells but not of Th1 cells or Th17 cells was enhanced in CD4+ T cells by the absence of A20. Consistently, enforced expression of A20 inhibited the differentiation of Th2 cells but not of Th1 cells or Th17 cells. Notably, the expression of GATA3 was significantly enhanced in A20-deficient CD4+ T cells, and the enhanced GATA3 expression was partly canceled by IL-2 neutralization. These results suggest that A20 functions as a stabilizing factor maintaining GATA3 levels during the induction of Th2 cells to prevent excessive Th2 cell differentiation.

A non-radioactive, improved PAR-CLIP and small RNA cDNA library preparation protocol.

Crosslinking and immunoprecipitation (CLIP) methods are powerful techniques to interrogate direct protein-RNA interactions and dissect posttranscriptional gene regulatory networks. One widely used CLIP variant is photoactivatable ribonucleoside enhanced CLIP (PAR-CLIP) that involves in vivo labeling of nascent RNAs with the photoreactive nucleosides 4-thiouridine (4SU) or 6-thioguanosine (6SG), which can efficiently crosslink to interacting proteins using UVA and UVB light. Crosslinking of 4SU or 6SG to interacting amino acids changes their base-pairing properties and results in characteristic mutations in cDNA libraries prepared for high-throughput sequencing, which can be computationally exploited to remove abundant background from non-crosslinked sequences and help pinpoint RNA binding protein binding sites at nucleotide resolution on a transcriptome-wide scale. Here we present a streamlined protocol for fluorescence-based PAR-CLIP (fPAR-CLIP) that eliminates the need to use radioactivity. It is based on direct ligation of a fluorescently labeled adapter to the 3'end of crosslinked RNA on immobilized ribonucleoproteins, followed by isolation of the adapter-ligated RNA and efficient conversion into cDNA without the previously needed size fractionation on denaturing polyacrylamide gels. These improvements cut the experimentation by half to 2 days and increases sensitivity by 10-100-fold.

Serum periostin levels serve as a biomarker for both eosinophilic airway inflammation and fixed airflow limitation in well-controlled asthmatics.

OBJECTIVE: Periostin, a matricellular protein, is produced from airway epithelial cells and lung fibroblasts by IL-13. It has been suggested that periostin is involved in allergic inflammation and fibrosis. However, the usefulness of serum periostin measurement in the assessment of airway inflammation and remodeling and management of asthmatic patients is still debated. We aimed to determine whether serum periostin levels reflect eosinophilic airway inflammation and airway remodeling in asthma. METHODS: We examined the relationship of serum periostin levels with clinical features, biomarkers for eosinophilic airway inflammation, fraction of exhaled nitric oxide (FeNO) levels and blood eosinophil counts, and pulmonary functions in 235 well-controlled asthmatic patients on inhaled corticosteroids (ICS) treatment. RESULTS: Serum periostin levels were positively correlated with blood eosinophil counts (%) and age (r = 0.36 and 0.23, respectively), and were negatively correlated with body weight and FEV1/FVC (%) (r = -0.24 and - 0.23, respectively) in well-controlled asthmatic patients on ICS treatment (daily dose of 453 µg equivalent to fluticasone propionate). Blood eosinophil counts and serum periostin levels were similarly associated with increased FeNO levels (≥40 ppb) in the asthmatics. Serum periostin levels were better associated with fixed airflow limitation (FEV1/FVC ratio <70%) than FeNO levels, blood eosinophil counts or total IgE levels in the asthmatics. Multivariate analysis showed that fixed airflow limitation was significantly associated with high serum periostin levels (≥97 ng/ml) (Odds ratio 3.2). CONCLUSIONS: Serum periostin levels serve as a biomarker for both eosinophilic airway inflammation and fixed airflow limitation in well-controlled asthmatics on ICS treatment.

Roles of alternatively activated M2 macrophages in allergic contact dermatitis.

Alternatively activated macrophages (M2 macrophages) play key roles in the suppression of Th1 cell responses and the orchestration of tissue repair. However, recent studies have shown that M2 macrophages have potentials to produce high levels of proinflammatory cytokines such as IL-1ß, IL-6, and TNF-α, suggesting that M2 macrophages may exacerbate inflammation in some settings. In this regard, we have recently shown that large numbers of M2 macrophages accumulate in the sites of hapten-induced contact hypersensitivity (CHS), an animal model of allergic contact dermatitis, and that M2 macrophages exacerbate hapten-induced CHS by producing matrix metalloproteinase 12 (MMP12). We have also shown that suppressor of cytokine signaling-3 (SOCS3), a member of SOCS family proteins that are cytokine-inducible negative regulators of the JAK/STAT signaling pathways, is highly and preferentially expressed in M2 macrophages in hapten-induced CHS and that SOCS3 expressed in M2 macrophages is involved in the attenuation of CHS by suppressing MMP12 production. These findings underscore the importance of M2 macrophage-derived MMP12 in the development of CHS, and suggest that inhibition of M2 macrophages or MMP12 could be a potential therapeutic strategy for the treatment of allergic contact dermatitis.

SOCS3 Expressed in M2 Macrophages Attenuates Contact Hypersensitivity by Suppressing MMP-12 Production.

Numerous studies have clarified the immunological mechanisms of contact hypersensitivity (CHS). In addition, we have recently shown that M2 macrophages play key roles in the development of CHS by producing matrix metalloproteinase-12 (MMP-12). However, regulatory mechanisms of the elicitation phase in CHS remain largely unknown. To determine the roles of suppressor of cytokine signaling (SOCS) family members in M2 macrophages in the regulation of CHS, we investigated the expression of SOCS family members in M2 macrophages at the inflammatory sites of CHS. Transcriptome analysis revealed that among SOCS family members, SOCS3 was highly expressed in M2 macrophages at the site of CHS, and SOCS3 induction was reduced by IFN-? neutralization. 2,4-Dinitrofluorobenzene-induced CHS was significantly enhanced and prolonged in mice lacking SOCS3 expression in monocytes/macrophages (SOCS3(?/?) mice) compared with that in control mice. Importantly, expression of MMP-12 in M2 macrophages was significantly increased in SOCS3(?/?) mice at the site of CHS, and deletion of the MMP-12 gene reduced the exacerbated CHS in SOCS3(?/?) mice. Finally, IFN-? inhibited IL-4-induced MMP-12 expression in a SOCS3-dependent manner. Taken together, these results suggest that SOCS3 expressed in M2 macrophages is involved in the attenuation and/or resolution of CHS, presumably by suppressing MMP-12 production.

Role of Bcl-3 in the development of follicular helper T cells and in the pathogenesis of rheumatoid arthritis.

OBJECTIVE: We have previously shown that expression of the Bcl-3 gene, a member of the IκB family, is down-regulated in CD4+ T cells from patients with rheumatoid arthritis (RA) following tocilizumab therapy. The objective of this study was to examine the role of Bcl-3 in the pathogenesis of RA. METHODS: DNA microarray analysis was used to compare the signal intensity of Bcl-3 in CD4+ T cells from untreated RA patients and healthy controls. We examined the roles of interleukin-6 (IL-6)/STAT-3 signaling in the induction of Bcl-3. In addition, we analyzed the gene expression profiles of Bcl-3-transduced CD4+ T cells by RNA sequencing. The effects of enforced expression as well as gene silencing of Bcl-3 on the development of follicular helper T (Tfh) cells were evaluated. Finally, we examined correlations between the signal intensities of Bcl-3 and Tfh cell-related genes in CD4+ T cells from untreated RA patients. RESULTS: Bcl-3 levels were significantly higher in RA patients than in healthy controls. IL-6 induced Bcl-3 expression in CD4+ T cells in a STAT-3-dependent manner. Transcriptome analysis revealed that the expression of Bcl-6, a master regulator of Tfh cell differentiation, was significantly up-regulated by the enforced Bcl-3 expression. The enforced Bcl-3 expression increased, but Bcl-3 silencing decreased, the numbers of IL-21-producing Tfh-like cells. Bcl-3 levels in CD4+ T cells from RA patients correlated positively with the levels of Tfh cell-related genes CXCR5, inducible costimulator, and achaete-scute homolog 2. CONCLUSION: Bcl-3 is involved in the development of Tfh cells and the pathogenesis of RA, presumably by inducing IL-21 production.

Helios Enhances Treg Cell Function in Cooperation With FoxP3.

OBJECTIVE: Helios+FoxP3+CD4+ (Helios+) Treg cells are believed to be involved in the regulation of various autoimmune diseases; however, the regulatory mechanisms underlying the development of Helios+ Treg cells remain uncertain. This study was undertaken to elucidate the regulatory mechanisms of Helios expression in CD4+ T cells and its roles in transforming growth factor ß (TGFß)-induced Treg cell function. METHODS: We examined the expression of Helios in CD4+ T cells in patients with rheumatoid arthritis by DNA microarray analysis before and after treatment with biologic agents. We also examined the effect of interleukin-6 (IL-6) and TGFß on Helios expression in CD4+ T cells in humans and mice. The effect of forced expression of Helios on murine induced Treg cell function was also examined. The role of FoxP3 in the induction and function of Helios was assessed by using CD4+ T cells from FoxP3-deficient scurfy mice. RESULTS: Tocilizumab, but not tumor necrosis factor (TNF) inhibitors or abatacept, increased Helios expression in CD4+ T cells in patients with a good response. IL-6 inhibited the TGFß-induced development of Helios+ induced Treg cells in both humans and mice. Both cell-intrinsic FoxP3 expression and TGFß signaling were required for Helios induction in murine induced Treg cells. The forced expression of Helios enhanced the expression of various Treg cell-related molecules and the suppressive function in murine induced Treg cells. Helios-mediated enhancement of the suppressive function of induced Treg cells was obvious in FoxP3-sufficient CD4+ T cells but not in FoxP3-deficient CD4+ T cells. CONCLUSION: Our findings indicate that Helios enhances induced Treg cell function in cooperation with FoxP3.

Roles of mast cells in the pathogenesis of inflammatory myopathy.

INTRODUCTION: In addition to the pivotal roles of mast cells in allergic diseases, recent data suggest that mast cells play crucial roles in a variety of autoimmune responses. However, their roles in the pathogenesis of autoimmune skeletal muscle diseases have not been clarified despite their distribution in skeletal muscle. Therefore, the objective of this study is to determine the roles of mast cells in the development of autoimmune skeletal muscle diseases. METHODS: The number of mast cells in the affected muscle was examined in patients with dermatomyositis (DM) or polymyositis (PM). The susceptibility of mast cell-deficient WBB6F1-Kit(W)/Kit(Wv) mice (W/W(v) mice) to a murine model of polymyositis, C protein-induced myositis (CIM), was compared with that of wild-type (WT) mice. The effect of mast cell reconstitution with bone marrow-derived mast cells (BMMCs) on the susceptibility of W/W(v) mice to CIM was also evaluated. RESULTS: The number of mast cells in the affected muscle increased in patients with PM as compared with patients with DM. W/W(v) mice exhibited significantly reduced disease incidence and histological scores of CIM as compared with WT mice. The number of CD8⁺ T cells and macrophages in the skeletal muscles of CIM decreased in W/W(v) mice compared with WT mice. Engraftment of BMMCs restored the incidence and histological scores of CIM in W/W(v) mice. Vascular permeability in the skeletal muscle was elevated in WT mice but not in W/W(v) mice upon CIM induction. CONCLUSION: Mast cells are involved in the pathogenesis of inflammatory myopathy.

Biological evaluation, chelation, and molecular modeling studies of novel metal-chelating inhibitors of NF-kappaB-DNA binding: structure activity relationships.

Previously, we have reported that aurintricarboxylic acid (ATA) is one of the most potent inhibitors of the DNA binding of transcription factor NF-kappaB. We now report the NF-kappaB-DNA binding inhibitory activity of ATA analogues. An electrophoretic mobility shift assay has shown that bromopyrogallol red (BPR) is the most effective inhibitor of NF-kappaB-DNA binding among the studied analogues. The molecular modeling studies showed that BPR makes a strong network of hydrogen bonds with the DNA-binding region of the p50 subunit of NF-kappaB and has electronegative potential on its peripheral surface. Because zinc has been reported to influence the DNA binding of NF-kappaB, the interaction of these analogues with zinc was studied. Chemical speciation and formation-constant studies showed that BPR forms the most stable 1:1 complex with zinc. BPR has also been found to be the most potent antioxidant among the studied analogues.

Inhibitory activity of polyhydroxycarboxylate chelators against recombinant NF-kappaB p50 protein-DNA binding.

The inhibitory effect of 7,8-dihydroxy-4-methylcoumarin (7,8-DHMC), 5,7-dihydroxy-4-methylcoumarin (5,7-DHMC), and gallic acid on the DNA binding of recombinant p50 protein and their interaction with zinc ion were studied. Electrophoretic mobility shift assay (EMSA) using p50 and biotin labeled DNA has shown that gallic acid is more effective than the dihydroxycoumarins in inhibiting the p50-DNA binding. Molecular modeling studies suggest an explanation for these observations. Effect of the addition of zinc after p50-DNA-binding inhibition by gallic acid was also studied. Chemical speciation and formation constant studies show that gallic acid forms a more stable 1:1 complex with zinc ion in comparison to the dihydroxycoumarins.