Staphylococcus aureus lysate induces an IgE response via memory B cells in nasal polyps.

BACKGROUND: Locally increased IgE levels plays a pathologic role in chronic rhinosinusitis with nasal polyps (CRSwNP). OBJECTIVE: This study aimed to investigate whether Staphylococcus aureus could induce aberrant IgE synthesis in CRSwNP and the potential mechanisms involved. METHODS: Total IgE, IL-4, IL-5, and IL-13 concentrations in the supernatants of the cultures stimulated with S aureus lysate were assessed by ELISA. S aureus-induced cellular responses were investigated by single-cell RNA sequencing. Flow cytometry and quantitative reverse transcription PCR were used to analyze B-cell subsets and stimulated cell ε-germline transcript expression, respectively. IgE-positive B-cell and germinal center localization were assessed by immunohistochemistry and immunofluorescence. RESULTS: S aureus lysate induced IgE production in the supernatants of nasal polyp (NP) tissues but not in those of healthy nasal mucosa. Moreover, IgE levels increased from days 2 to 4 after stimulation, paralleling the enhanced ε-germline transcript, IL-5, and IL-13 expression. Single-cell RNA sequencing revealed that there were increased IL-5 and IL-13 in group 2 innate lymphoid cells and identified a clonal overlap between unstimulated memory B cells and S aureus-stimulated plasma cells. The enriched IgE within NPs was mainly produced by IgE-negative memory B cells. Cellular evidence indicated that the IgE memory response to S aureus might also exist in the peripheral blood of CRSwNP patients. The S aureus-induced IgE memory response was associated with elevated IgE levels in NPs, asthma, and postoperative CRSwNP recurrence. CONCLUSIONS: S aureus induced an IgE response via IgE-negative memory B cells in CRSwNP patients, possibly contributing to CRSwNP development.

Airways epithelial exposure to Streptococcus pneumoniae in the presence of the alarmin IL-33 induces a novel subset of pro-inflammatory ILC2s promoting a mixed inflammatory response.

BACKGROUND: We have previously shown that asthma-like airways inflammation may be induced by topical exposure to respiratory tract pathogens such as S. pneumoniae (SP) in concert with epithelial alarmins such as IL-33. Details of the pathogenesis of this murine surrogate remain however unexplored. METHODS: Airways inflammation was induced by repeated, intranasal exposure of Il-4-/-, Rag1-/- and Rag2-/-Il2rg-/- mice (in which B lymphocyte IgE switching, adaptive and innate immunity are respectively ablated) as well as wild type mice to inactivated SP, IL-33 or both. Airways pathological changes were analysed, and the subsets and functions of locally accumulated ILC2s investigated by single cell RNA sequencing and flow cytometry. RESULTS: In the presence of IL-33, repeated exposure of the airways to inactivated SP caused marked eosinophil- and neutrophil-rich inflammation and local accumulation of ILC2s, which was retained in the Il-4-/- and Rag1-/- deficient mice but abolished in the Rag2-/-Il2rg-/- mice, an effect partly reversed by adoptive transfer of ILC2s. Single cell sequencing analysis of ILC2s recruited following SP and IL-33 exposure revealed a Klrg1+Ly6a+subset, expressing particularly elevated quantities of the pro-inflammatory cytokine IL-6, type 2 cytokines (IL-5 and IL-13) and MHC class II molecules, promoting type 2 inflammation as well as involved in neutrophil-mediated inflammatory responses. CONCLUSION: Local accumulation of KLRG1+Ly6a+ ILC2s in the lung tissue is a critical aspect of the pathogenesis of airways eosinophilic and neutrophil-rich inflammation induced by repeated exposure to SP in the presence of the epithelial alarmin IL-33.

Attenuated airways inflammation and remodeling in IL-37a and IL-37b transgenic mice with an ovalbumin-induced chronic asthma.

BACKGROUND: Asthma is a common chronic respiratory disease characterized by airways inflammation, hyperresponsiveness and remodeling. IL-37, an anti-inflammatory cytokine, consists of five splice isoforms, that is, a-e. Although it has been previously shown that recombinant human IL-37b is able to inhibit airway inflammation and hyperresponsiveness in animal models of asthma, the effects and difference of other IL-37 isoforms, such as IL-37a on features of asthma are unknown. METHODS: Animal models of chronic asthma were established using IL-37a and IL-37b transgenic mice with C57BL/6J background and wild-type (WT) mice sensitized and nasally challenged with ovalbumin (OVA). Airway hyperresponsiveness was measured using FlexiVent apparatus, while histological and immunohistological stainings were employed to measure airways inflammation and remodeling indexes, including goblet cell metaplasia, mucus production, deposition of collagen, hypertrophy of airway smooth muscles and pulmonary angiogenesis. RESULTS: Compared to WT mice, both IL-37a and IL-37b transgenic mice had significant reduced airway hyperresponsiveness and the declined total numbers of inflammatory cells, predominant eosinophils into airways and lung tissues. Furthermore, all features of airways remodeling, including degrees of mucus expression, collagen deposition, hypertrophy of smooth muscles, thickness of airways and neovascularization markedly decreased in IL-37 transgenic mice compared with OVA-treated WT mice. CONCLUSION: Our data suggest that both IL-37a and IL-37b isoforms are able to not only ameliorate airways inflammation and airways hyperresponsiveness, but also greatly reduce airways structural changes of animal models of chronic asthma.

Repeated exposure to inactivated Streptococcus pneumoniae induces asthma-like pathological changes in mice in the presence of IL-33.

While environmental aeroallergens and epithelial alarmins such as IL-33 are firmly implicated in asthma, the possible role of Streptococcus pneumoniae (S. pneumoniae) antigens is less clear. To explore this, wild-type BALB/c mice were repeatedly challenged per-nasally with IL-33 and inactivated S. pneumoniae, either agent alone or diluent control. Some animals were rested then later re-challenged with inactivated S. pneumoniae alone. Serum concentrations of S. pneumoniae lysates-specific IgE were measured in patients with asthma and control subjects. Interestingly, in the presence of IL-33, repeated exposure to inactivated S. pneumoniae induced asthma-like pathological changes accompanied by a systemic adaptive immune response. Subsequent re-exposure of the sensitized animals to inactivated S. pneumoniae alone was able to induce such changes. The concentration of S. pneumoniae lysates-specific IgE was significantly elevated in the asthma patients. These data suggest that antigens derived from infectious microorganisms may participate in generating the mucosal inflammation which characterizes asthma.

IL-33 induced airways inflammation is partially dependent on IL-9.

Asthma is an inflammatory disease of the airways and numerous cytokines contribute to this pathogenesis. It is shown that challenge of airways with IL-33 induces asthma-like pathological changes in mice, but the possible downstream cytokines in this process remain to be characterised. To explore this, we compared changes in the airways of wildtype (WT) and IL-9 deficient mice challenged with IL-33. In line with previous report, per-nasal challenge of WT mice with IL-33 significantly increased the responsiveness of the airways along with infiltration of inflammatory cells, goblet cell hyperplasia, collagen deposition and smooth muscle hypertrophy, and the expression of cytokines compared with control group. Surprisingly, all of these pathological changes were significantly attenuated in IL-9 deficient mice following identical IL-33 challenge. These data suggest that IL-9 is one downstream cytokine relevant to the effects of IL-33 in asthmatic airways and consequently a potential therapeutic target for the treatment of asthma.

Cigarette smoke aggravates asthma via altering airways inflammation phenotypes and remodelling.

INTRODUCTION: Many asthmatic patients are exposed to cigarette smoke actively or passively, which contributes to asthma exacerbation and poor control. This study is to explore the effects of cigarette smoke on pathological changes in murine surrogate of asthma. METHODS: C57BL/6 mice were sensitised and challenged with ovalbumin (OVA) to establish a surrogate of asthma and then administered with cigarette smoke extract (CSE). Airways hyperresponsiveness (AHR) was measured using the Flexivent system. Histological staining (haematoxylin-eosin [HE], periodic acid Schiff [PAS], Congo red and Masson's trichrome) was employed to measure pathological changes in sections of lung tissue of experimental mice. Enzyme-linked immunosorbent assay (ELISA) was used to measure the concentrations of total and OVA-specific IgE, cytokines and chemokines (eotaxin-1, IL-13, IL-1ß, TNF-α, IL-17A, IL-33) in the lung tissue homogenates. Immunoreactivity for vWF and α-SMA in lung tissue sections was detected by immunohistochemistry. RESULTS: Exposure of the animals to CSE significantly reduced OVA-induced AHR, the number of eosinophils in bronchoalveolar lavage fluid (BALF) and eosinophils infiltrating into the lung tissue, as well as concentrations of some cytokines in lung homogenate. In contrast, it significantly enhanced the number of macrophages and M2 in BALF, as well as collagen deposition, smooth muscle thickness and alveolar destruction in lung tissue. CONCLUSION: CSE inhibits OVA-induced AHR, changes inflammation 'phenotypes', while accelerates some aspects of airways remodelling, which might contribute to worse symptoms and be refractory to anti-inflammation therapies for asthmatics.