Masaya Yokota

Dectin-2 Promotes House Dust Mite–Induced T Helper Type 2 and Type 17 Cell Differentiation and Allergic Airway Inflammation in Mice

The fact that sensitization against fungi is closely related to the severity of asthma suggests that immune systems recognizing fungi are involved in the pathogenesis of severe asthma. Recently, Dectin-2 (gene symbol, Clec4n), a C-type lectin receptor, has been shown to function as not only a major pattern-recognition receptor for fungi, but also a receptor for some components of house dust mite (HDM) extract, a major allergen for asthma. However, the roles of Dectin-2 in the induction of HDM-induced allergic airway inflammation remain largely unknown. Our objective was to determine the roles of Dectin-2 in HDM-induced allergic airway inflammation. We examined the roles of Dectin-2 in the induction of HDM-induced T helper (Th) 2 and Th17 cell differentiation and subsequent allergic airway inflammation by using Clec4n-deficient (Clec4n(-/-)) mice. We also investigated Dectin-2-expressing cells in the lung and their roles in HDM-induced allergic airway inflammation. Clec4n(-/-) mice showed significantly attenuated HDM-induced allergic airway inflammation and decreased Th2 and Th17 cell differentiation. Dectin-2 mRNA, together with Dectin-3 and Fc receptor-γ mRNAs, was expressed in CD11b(+) dendritic cells (DCs), but not in CD4(+) T cells or epithelial cells in the lung. CD11b(+) DCs isolated from Clec4n(-/-) mice expressed lower amounts of proinflammatory cytokines and costimulatory molecules, which could lead to Th2 and Th17 cell differentiation than those from wild-type mice. HDM-pulsed Clec4n(-/-) DCs were less efficient for the induction of allergic airway inflammation than HDM-pulsed wild-type DCs. In conclusion, Dectin-2 expressed on CD11b(+) DCs promotes HDM-induced Th2 and Th17 cell differentiation and allergic airway inflammation.

[18F]FDG uptake in proximal muscles assessed by PET/CT reflects both global and local muscular inflammation and provides useful information in the management of patients with polymyositis/dermatomyositis

OBJECTIVE This study aimed to determine whether [(18)F]fluorodeoxyglucose-PET/CT ([(18)F]FDG-PET/CT) discriminates PM/DM from non-muscular diseases and also whether FDG uptake in proximal muscles reflects the activity and severity of muscular inflammation in PM/DM. METHODS Twenty treatment-naïve PM/DM patients who underwent [(18)F]FDG-PET/CT were retrospectively identified by reviewing medical records. The same number of age- and sex-matched control patients with non-muscular diseases were also identified. Standardized uptake value (SUV) was calculated for each of the seven proximal muscles. For patient-based assessment, mean proximal muscle SUV was calculated by averaging the SUVs for these proximal muscles bilaterally. RESULTS Mean proximal muscle SUVs were significantly greater in PM/DM patients than in control patients (median 1.05 vs 0.69, P < 0.001). Mean proximal muscle SUVs significantly correlated with mean proximal manual muscle test scores (ρ = 0.49, P = 0.028) and serum levels of creatine kinase (ρ = 0.54, P = 0.015) and aldolase (ρ = 0.64, P = 0.002). Furthermore, SUVs in proximal muscles from which biopsy specimens were obtained significantly correlated with histological grade for inflammatory cell infiltration (ρ = 0.66, P = 0.002). CONCLUSION Our results suggest that [(18)F]FDG-PET/CT is useful in the diagnosis of PM/DM when inflammation in proximal muscles is globally assessed with quantitative measurements. Our results also indicate that local FDG uptake in a proximal muscle reflects the activity of inflammation in the same muscle and provides useful information in determining the region for muscle biopsy.

Tumor Suppressor p53 Inhibits Systemic Autoimmune Diseases by Inducing Regulatory T Cells

The tumor suppressor p53 plays a central role in tumor suppression by inducing apoptosis, cell cycle arrest, senescence, and DNA repair. In addition to the antitumor functions of p53, accumulating evidence using systemic p53-deficient mice suggests that p53 suppresses autoimmunity. However, it remains unknown how p53 suppresses autoimmunity. In this study, we generated T cell–specific p53-deficient mice (CD4-Cre p53fl/fl mice, or p53 conditional knockout [cKO] mice) and found that aged p53-cKO mice spontaneously developed inflammatory lesions in various organs, including lung, liver, stomach, thyroid gland, submandibular gland, and kidney. Additionally, anti-nuclear Abs and autoantibodies against gastric parietal cells were detected in p53-cKO mice but not in control p53fl/fl mice (p53 wild-type mice). Importantly, the number of Foxp3+CD4+ regulatory T cells (Tregs) in the spleen and lung as well as in vitro differentiation of induced Tregs was significantly reduced in p53-cKO mice as compared with that in p53 wild-type mice. Regarding the mechanisms underlying p53-mediated Treg induction, p53 enhanced the transcription of Foxp3 by binding to the promoter and the conserved noncoding DNA sequence-2 of the Foxp3 gene. Taken together, these results suggest that p53 expressed in T cells functions as a suppressor for autoimmunity by inducing Treg differentiation.

Dectin-1 Plays an Important Role in House Dust Mite–Induced Allergic Airway Inflammation through the Activation of CD11b+ Dendritic Cells

It is well known that sensitization against fungi is closely associated with severity of asthma. Dectin-1 (gene symbol Clec7a), a C-type lectin receptor, recognizes the fungal cell wall component β-glucan, as well as some component(s) in house dust mite (HDM) extract. However, the roles of Dectin-1 in HDM-induced allergic airway inflammation remain unclear. In this study, we used Dectin-1–deficient (Clec7a−/−) mice to examine whether Dectin-1 is involved in HDM-induced allergic airway inflammation. We found that HDM-induced eosinophil and neutrophil recruitment into the airways was significantly attenuated in Clec7a−/− mice compared with that in wild-type mice. In addition, HDM-induced IL-5, IL-13, and IL-17 production from mediastinum lymph node cells was reduced in HDM-sensitized Clec7a−/− mice. Dectin-1 was expressed on CD11b+ dendritic cells (DCs), an essential DC subset for the development of allergic inflammation, but not on CD103+ DCs, plasmacytoid DCs, or lung epithelial cells. Transcriptome analysis revealed that the expression of chemokine/chemokine receptors, including CCR7, which is indispensable for DC migration to draining lymph nodes, was decreased in Clec7a−/− DCs. In accordance with these results, the number of HDM-labeled CD11b+ DCs in mediastinum lymph nodes was significantly reduced in Clec7a−/− mice compared with wild-type mice. Taken together, these results suggest that Dectin-1 expressed on CD11b+ DCs senses some molecule(s) in HDM extract and plays a critical role in the induction of HDM-induced allergic airway inflammation by inducing the expression of chemokine/chemokine receptors in DCs.

T-bet inhibits innate lymphoid cell–mediated eosinophilic airway inflammation by suppressing IL-9 production

Background: Innate lymphoid cells (ILCs) are emerging subsets of immune cells that produce large amounts of cytokines upon cytokine and/or alarmin stimulation. Recent studies have shown that T‐bet plays pivotal roles in the development of ILC3s and type 1 ILCs; however, the roles of T‐bet in lung type 2 innate lymphoid cells (ILC2s) remain unknown. Objective: We sought to determine the role of T‐bet in ILC2‐mediated airway inflammation. Methods: The expression of T‐bet in lung ILCs (defined as Thy1.2+ Lin− cells) was examined. The roles of T‐bet in the development of lung ILC2s and airway inflammation induced by IL‐33 administration were examined by using T‐bet–deficient (T‐bet−/−) mice. Gene expression profiles of T‐bet−/− lung ILCs were analyzed by RNA sequencing. Results: T‐bet was expressed in lung ILC2s (defined as Thy1.2+ Lin− cells expressing ST2 or CD25) and IFN‐&ggr; enhanced its expression. Although the development of lung ILC2s at steady‐state conditions was normal in T‐bet−/− mice, IL‐33–induced accumulation of lung ILC2s and eosinophilic airway inflammation were exacerbated in T‐bet−/− mice. The exacerbated accumulation of ILC2s and eosinophilic airway inflammation by the absence of T‐bet were evident even in a RAG2−/− background, suggesting that T‐bet expressed in non–T/non–B population is involved in the suppression of IL‐33–induced eosinophilic airway inflammation. Transcriptome analysis revealed that IL‐9 expression in IL‐33–stimulated lung ILCs was upregulated in T‐bet−/− mice compared with that in wild‐type mice. Importantly, neutralization of IL‐9 markedly attenuated IL‐33–induced accumulation of lung ILC2s and eosinophilic inflammation in T‐bet−/− mice. Conclusions: T‐bet suppresses IL‐9 production from lung ILC2s and thereby inhibits IL‐33–induced eosinophilic airway inflammation.

Roles of mast cells in the pathogenesis of inflammatory myopathy

IntroductionIn 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.MethodsThe 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-KitW/KitWv mice (W/Wv 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/Wv mice to CIM was also evaluated.ResultsThe number of mast cells in the affected muscle increased in patients with PM as compared with patients with DM. W/Wv 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/Wv mice compared with WT mice. Engraftment of BMMCs restored the incidence and histological scores of CIM in W/Wv mice. Vascular permeability in the skeletal muscle was elevated in WT mice but not in W/Wv mice upon CIM induction.ConclusionMast cells are involved in the pathogenesis of inflammatory myopathy.

STAT4 Is Required for IFN-β-Induced MCP-1 mRNA Expression in Murine Mast Cells

Background: Mast cells are immunocompetent cells that are found in almost all tissues and function as sentinels of immune responses. Recently, it has been shown that mast cells play significant roles in innate immune responses. However, it is still largely unknown whether signal transducers and activators of transcription 4 (STAT4), one of the STAT proteins under type I IFN signaling, is involved in type I IFN-mediated gene expression in mast cells. Methods: We investigated the role of STAT4 in IFN-β-induced gene expression in mast cells by using STAT4-deficient (STAT4–/–) bone marrow-derived mast cells (BMMCs). Results: STAT4 was expressed in BMMCs and activated in response to IFN-β but not to IL-12 or IL-23. The development of BMMCs as well as IgE-induced degranulation of BMMCs was normal in STAT4–/– mice. On the other hand, while IFN-β-induced mRNA expression of interferon-induced protein with tetratricopeptide repeats 1 (IFIT-1), protein kinase interferon-inducible double stranded RNA dependent (PKR), and myxovirus resistance 1 (Mx1) was similar between STAT4–/– BMMCs and wild-type (WT) BMMCs, IFN-β-induced MCP-1 mRNA expression was severely diminished in STAT4–/– BMMCs as compared with WT BMMCs. Conclusions: STAT4 plays an essential role in IFN-β-induced MCP-1 mRNA expression in mast cells.

IκBNS induces Muc5ac expression in epithelial cells and causes airway hyper-responsiveness in murine asthma models

In allergic asthma, environmental allergens including house dust mite (HDM) trigger pattern recognition receptors and activate downstream signaling pathways including NF‐κB pathways not only in immune cells but also in airway epithelial cells. Recent studies have shown that NF‐κB activation is regulated positively or negatively depending on the cellular context by IκBNS (encoded by the gene Nfkbid), one of atypical IκB proteins, in the nucleus. Therefore, we hypothesized that IκBNS expressed in immune cells or epithelial cells is involved in the regulation of asthmatic responses.

Tumor Suppressor p53 Functions as a Negative Regulator in IgE-Mediated Mast Cell Activation

Mast cells are known to play a pivotal role in allergic diseases such as allergic rhinitis, asthma, and atopic dermatitis by releasing granules containing histamine, LTC4, and other preformed chemical mediators. Previous reports have demonstrated that IKK2 (also called IKKβ), a central intracellular component of NF-κB activation pathways, plays a critical role in IgE-mediated degranulation of mast cells and anaphylaxis in mice. In this study, we show that protein levels of tumor suppressor p53 are up-regulated upon IgE-mediated activation in mast cells and lack of p53 results in enhanced responses in both early and late phase anaphylaxis. p53 inhibits not only the catalytic activity of IKK2 presumably through the modulation of glycosylation but also p65 (RelA)-mediated transactivation. Our findings are the first to demonstrate that p53 functions as a negative regulator in mast cells.

Synovitis and osteitis in the left sternoclavicular joint in a 60-year-old woman

A 60-year-old woman underwent ultrasonography for swollen and tender sternoclavicular joints and stiffness in the bilateral hands. Ultrasound revealed severe synovial hypertrophy that accompanied markedly increased power Doppler signals in the left sternoclavicular joint (Fig. 1a, b). In contrast, synovitis was absent in the wrists and fingers (Fig. 1c, d). [F] FDG-PET/CT revealed hyperostosis and marked accumulation of [F] FDG in the bones of the left sternoclavicular joint (Fig. 2) but no inflammation in the axial or peripheral joints. This patient was diagnosed with SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome when she developed genital acne 6 weeks after the imaging investigations. The presence of both synovitis and hyperostosis in the sternoclavicular joint, which is one of the most frequently involved joints in SAPHO syndrome [1], and no involvement of the axial or peripheral joints demonstrated by two different imaging modalities strongly favored the diagnosis of SAPHO syndrome over seronegative rheumatoid arthritis or spondyloarthropathy even before the emergence of skin manifestation. Although ultrasound neither can detect inflammation under the bone surface nor is the best imaging tool to assess axial joints, it determines the distribution pattern of joints with synovitis more accurately than clinical examination does [2]. Since ultrasound is much less costly and more accessible than other imaging modalities capable of wholebody joint assessment such as FDG-PET and MRI, ultrasound can be a good initial imaging tool in daily practice to distinguish arthritic conditions that involve the anterior chest wall.