Miyuki Tsuda

B7-DC Regulates Asthmatic Response by an IFN-γ-Dependent Mechanism

B7-H1 (PD-L1) and B7-DC (PD-L2) are the ligands for programmed death-1 (PD-1), which is a member of the CD28/CTLA-4 family and has been implicated in peripheral tolerance. We investigated the roles of B7-H1 and B7-DC in a murine OVA-induced allergic asthma model. B7-H1 was constitutively expressed on dendritic cells, macrophages, B cells, and T cells in the lungs of naive mice, and its expression could be dramatically increased after allergen challenge. In contrast, B7-DC expression was scarcely expressed on dendritic cells in naive mice, but was up-regulated after allergen challenge, although the up-regulation of B7-DC expression on macrophages was minimal. Treatment of mice with anti-B7-DC mAb at the time of allergen challenge, but not at the time of sensitization, significantly increased their airway hyper-reactivity and eosinophilia. Such treatment also resulted in the increased production of IL-5 and IL-13, and decreased IFN-γ production in the lungs and draining lymph node cells. These changes were diminished when mice were depleted of IFN-γ by anti-IFN-γ mAb pretreatment. Interestingly, treatment with anti-B7-H1 or anti-PD-1 mAb did not significantly affect the asthmatic response. These results suggest a unique role for B7-DC in the regulation of asthmatic response through an IFN-γ-dependent, but PD-1-independent, mechanism.

Exacerbation of Experimental Allergic Asthma by Augmented Th2 Responses in WSX-1-Deficient Mice

WSX-1 (IL-27R) is a class I cytokine receptor with homology to gp130 and IL-12 receptors and is typically expressed on CD4+ T lymphocytes. Although previous reports have clarified that IL-27/WSX-1 signaling plays critical roles in both Th1 differentiation and attenuation of cell activation and proinflammatory cytokine production during some bacterial or protozoan infections, little is known about the importance of WSX-1 in cytokine-mediated diseases of allergic origin. To this aim, we took advantage of WSX-1-deficient (WSX-1−/−) mice and induced experimental asthma, in which Th2 cytokines are central modulators of the pathology. OVA-challenged WSX-1−/− mice showed marked enhancement of airway responsiveness with goblet cell hyperplasia, pulmonary eosinophil infiltration, and increased serum IgE levels compared with wild-type mice. Production of Th2 cytokines, which are largely responsible for the pathogenesis of asthma, was augmented in the lung or in the culture supernatants of peribronchial lymph node CD4+ T cells from WSX-1−/− mice compared with those from wild-type mice. Surprisingly, IFN-γ production was also enhanced in WSX-1−/− mice, albeit at a low concentration. The cytokine overproduction, thus, seems independent from the Th1-promoting property of WSX-1. These results demonstrated that IL-27/WSX-1 also plays an important role in the down-regulation of airway hyper-reactivity and lung inflammation during the development of allergic asthma through its suppressive effect on cytokine production.

Spred-1 negatively regulates allergen-induced airway eosinophilia and hyperresponsiveness

T helper 2 cytokines, including interleukin (IL)-4, IL-5, and IL-13, play a critical role in allergic asthma. These cytokines transmit signals through the Janus kinase/signal transducer and activator of transcription (STAT) and the Ras–extracellular signal-regulated kinase (ERK) signaling pathways. Although the suppressor of cytokine signaling (SOCS) family proteins have been shown to regulate the STAT pathway, the mechanism regulating the ERK pathway has not been clarified. The Sprouty-related Ena/VASP homology 1–domain-containing protein (Spred)-1 has recently been identified as a negative regulator of growth factor–mediated, Ras-dependent ERK activation. Here, using Spred-1–deficient mice, we demonstrated that Spred-1 negatively regulates allergen-induced airway eosinophilia and hyperresponsiveness, without affecting helper T cell differentiation. Biochemical assays indicate that Spred-1 suppresses IL-5–dependent cell proliferation and ERK activation. These data indicate that Spred-1 negatively controls eosinophil numbers and functions by modulating IL-5 signaling in allergic asthma.

Decrease of Interleukin-10-Producing T Cells in the Peripheral Blood of Severe Unstable Atopic Asthmatics

Background: Although IL-10 is known as an immunoregulatory cytokine produced by various cells including T cells, its basic profile in atopic asthma remains uncertain. Objective: The profiles of IL-10 production in circulating CD4+ T cells of atopic asthmatics were investigated with respect to clinical severity. Methods: Forty atopic asthmatics were divided into three groups: mild, and severe but stable and severe unstable asthmatics. Eosinophils were counted in the peripheral blood and sputum, and exhaled nitric oxide was assessed. PBMCs were stimulated with or without anti-CD3 and anti-CD28 antibodies and then processed for detecting IL-10-producing CD4+ cells using flow cytometry. Results: There was no difference in the eosinophil count in blood or sputum and in nitric oxide level among the three groups. IL-10-producing CD4+ cells were mainly detected in a CD45RO+ memory population. The frequency of IL-10-producing cells after stimulation was significantly lower in the severe unstable group compared to the mild group. In addition, the frequency of IL-10-producing cells in the severe unstable group was significantly lower than that in the severe stable group despite the fact that both groups received similar treatments with high-dose inhaled corticosteroids. The IL-10 production of CD4+CD45RO+ cells in response to dexamethasone did not differ among the three groups. Conclusions: IL-10-producing CD4+CD45RO+ cells in the peripheral blood are decreased in severe unstable asthmatics, which is not explained by the effect of high-dose inhaled corticosteroid medication.

Different roles of interleukin-10 in onset and resolution of asthmatic responses in allergen-challenged mice.

Objective:  Although interleukin (IL)‐10 is an immunoregulatory cytokine produced by various cells including T cells, its precise role in asthma remains uncertain. The aim of this study was to investigate the role of IL‐10 in experimental asthma using ovalbumin (OVA)‐sensitized mice.

Effects of Salmeterol in Patients with Persistent Asthma Receiving Inhaled Corticosteroid plus Theophylline

Background: Patients with severe asthma require multiple therapies to improve lung function and reduce symptoms. The use of long-acting inhaled β2-agonists plus theophylline in addition to high doses of inhaled corticosteroids (ICSs) for the treatment of severe asthma has not been extensively studied. Objective: The purpose of this study was to investigate the efficacy and safety of salmeterol combined with high-dose ICSs plus theophylline in severe asthma. Methods: We undertook a randomized, placebo-controlled, crossover study to compare the effect of a single dose of inhaled salmeterol (50 µg) or a placebo in patients with severe asthma whose conditions were not being adequately controlled by therapies with high-dose ICSs plus oral theophylline with or without leukotriene receptor antagonists. Results: Twenty patients took part in the trial. Compared with the placebo, the inhalation of salmeterol significantly increased the FEV1. Even in the 9 patients treated with high-dose ICSs plus theophylline plus a leukotriene receptor antagonist, the FEV1 increased significantly more after salmeterol than after the placebo. Conclusion: Patients with severe asthma receiving high-dose ICSs plus theophylline may benefit from the addition of salmeterol.

Different Profiles of IL-10+IFN-γ–IL-4–CD4+ T Cells in the Peripheral Blood in Atopic and Non-Atopic Asthmatics

Background: The impaired production of interleukin (IL) 10 from regulatory T cells has been proposed as a causal mechanism of asthma. Although IL-10-producing (IL-10+) T cells are detectable in the peripheral blood, their significance in the pathophysiology of asthma remains uncertain. Objectives: This study aimed to investigate the profile of circulating IL-10+CD4+ T cells in atopic and non-atopic asthma. Methods: Atopic and non-atopic asthmatics were divided into a mild and severe group. Their peripheral blood mononuclear cells (PBMCs) were stimulated with anti-CD3 and anti-CD28 antibodies and then processed for triple cytokine flow cytometry directed to IL-10, interferon (IFN) γ and IL-4. Results: IL-10+CD4+ cells were exclusively detected in the IFN-γ–IL-4– population. In atopic asthma, the frequency of IL-10+IFN-γ–IL-4–CD4+ cells in the severe group was significantly lower than that in the mild group. The frequency of IL-10+IFN-γ–IL-4–CD4+ cells in the severe group was not significantly different from that in the mild group of those with non-atopic asthma. The frequency of IL-4+IFN-γ–IL-10–CD4+ cells (Th2) was significantly higher in the group with mild atopic asthma than in that with mild non-atopic asthma. IFN-γ+IL-4–IL-10–CD4+ cells (Th1) did not differ between groups, irrespective whether the subjects suffered from atopic or non-atopic asthma. Conclusions: IL-10+CD4+ cells in PBMCs may be distinct from Th1 or Th2 and likely have the profile of regulatory T cells. The differential association of IL-10+IFN-γ–IL-4–CD4+ cells with clinical severity between atopic and non-atopic asthma implies that its pathophysiological significance may differ among asthma phenotypes.