The immunology of asthma
TL;DR: Results from in-depth molecular studies of mouse models in light of the results from the first clinical trials targeting key cytokines in humans are discussed and the extraordinary heterogeneity of asthma is described.
Abstract: Asthma is a common disease that affects 300 million people worldwide. Given the large number of eosinophils in the airways of people with mild asthma, and verified by data from murine models, asthma was long considered the hallmark T helper type 2 (T(H)2) disease of the airways. It is now known that some asthmatic inflammation is neutrophilic, controlled by the T(H)17 subset of helper T cells, and that some eosinophilic inflammation is controlled by type 2 innate lymphoid cells (ILC2 cells) acting together with basophils. Here we discuss results from in-depth molecular studies of mouse models in light of the results from the first clinical trials targeting key cytokines in humans and describe the extraordinary heterogeneity of asthma.
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TL;DR: The general mechanisms of how different stimuli trigger type-2-cell-mediated immunity at mucosal barriers are reviewed and how this leads to protection or disease are reviewed.
583 citations
Cites background from "The immunology of asthma"
...Nevertheless, the type-2-cellmediated response can also be very detrimental; for example, the smooth muscle contraction and mucus production after inhalation of harmless allergens leads to chronic airway narrowing in asthma and can also cause acute death in anaphylaxis (Lambrecht and Hammad, 2015)....
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TL;DR: Recent developments on IL-1 to IL-38, TNF-α, TGF-β, and interferons are reviewed and their cellular sources, targets, receptors, signaling pathways, and roles in immune regulation in patients with allergy and asthma and other inflammatory diseases are discussed.
Abstract: There have been extensive developments on cellular and molecular mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections during the last few years. Better understanding the functions, reciprocal regulation, and counterbalance of subsets of immune and inflammatory cells that interact through interleukins, interferons, TNF-α, and TGF-β offer opportunities for immune interventions and novel treatment modalities in the era of development of biological immune response modifiers particularly targeting these molecules or their receptors. More than 60 cytokines have been designated as interleukins since the initial discoveries of monocyte and lymphocyte interleukins (called IL-1 and IL-2, respectively). Studies of transgenic or gene-deficient mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided essential information about their functions. Here we review recent developments on IL-1 to IL-38, TNF-α, TGF-β, and interferons. We highlight recent advances during the last few years in this area and extensively discuss their cellular sources, targets, receptors, signaling pathways, and roles in immune regulation in patients with allergy and asthma and other inflammatory diseases.
560 citations
Cites background from "The immunology of asthma"
...However, when allergens have additional protease activity and/or are accompanied by microbial components, such as endotoxins or inorganic particles, epithelial secretory responses can lead to mixed TH2 and TH17 immunity or even TH1 responses.(42,43) In response to viruses, epithelial cells produce a wide range of mediators, such as type I interferons, GM-CSF, RANTES/CCL5, and IFN-g–induced protein 1/CXCL10....
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TL;DR: The cytokine networks driving asthma are reviewed, placing these in cellular context and incorporating insights from cytokine-targeting therapies in the clinic, to argue that the development of new and improved therapeutics will require understanding the diverse mechanisms underlying the spectrum of asthma pathologies.
501 citations
TL;DR: It is shown that chronic exposure to low-dose endotoxin or farm dust protects mice from developing house dust mite–induced asthma, and a single-nucleotide polymorphism in the gene encoding A20 was associated with allergy and asthma risk in children growing up on farms.
Abstract: Growing up on a dairy farm protects children from allergy, hay fever, and asthma. A mechanism linking exposure to this endotoxin (bacterial lipopolysaccharide)-rich environment with protection has remained elusive. Here we show that chronic exposure to low-dose endotoxin or farm dust protects mice from developing house dust mite (HDM)-induced asthma. Endotoxin reduced epithelial cell cytokines that activate dendritic cells (DCs), thus suppressing type 2 immunity to HDMs. Loss of the ubiquitin-modifying enzyme A20 in lung epithelium abolished the protective effect. A single-nucleotide polymorphism in the gene encoding A20 was associated with allergy and asthma risk in children growing up on farms. Thus, the farming environment protects from allergy by modifying the communication between barrier epithelial cells and DCs through A20 induction.
458 citations
TL;DR: Functional skewing of monocyte/macrophage polarization occurs in physiological conditions as well as in pathology and is now considered a key determinant of disease development and/or regression.
Abstract: Macrophages are cells of the innate immunity constituting the mononuclear phagocyte system and endowed with remarkable different roles essential for defense mechanisms, development of tissues, and homeostasis. They derive from hematopoietic precursors and since the early steps of fetal life populate peripheral tissues, a process continuing throughout adult life. Although present essentially in every organ/tissue, macrophages are more abundant in the gastro-intestinal tract, liver, spleen, upper airways, and brain. They have phagocytic and bactericidal activity and produce inflammatory cytokines that are important to drive adaptive immune responses. Macrophage functions are settled in response to microenvironmental signals, which drive the acquisition of polarized programs, whose extremes are simplified in the M1 and M2 dichotomy. Functional skewing of monocyte/macrophage polarization occurs in physiological conditions (e.g., ontogenesis and pregnancy), as well as in pathology (allergic and chronic inflammation, tissue repair, infection, and cancer) and is now considered a key determinant of disease development and/or regression. Here, we will review evidence supporting a dynamic skewing of macrophage functions in disease, which may provide a basis for macrophage-centered therapeutic strategies.
450 citations
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TL;DR: Atopic asthma is associated with activation in the bronchi of the interleukin-3, 4, and 5 and GM-CSF gene cluster, a pattern compatible with predominant activation of the TH2-like T-cell population.
Abstract: Background. In atopic asthma, activated T helper lymphocytes are present in bronchial-biopsy specimens and bronchoalveolar-lavage (BAL) fluid, and their production of cytokines may be important in the pathogenesis of this disorder. Different patterns of cytokine release are characteristic of certain subgroups of T helper cells, termed TH1 and TH2, the former mediating delayed-type hypersensitivity and the latter mediating IgE synthesis and eosinophilia. The pattern of cytokine production in atopic asthma is unknown. Methods. We assessed cells obtained by BAL in subjects with mild atopic asthma and in normal control subjects for the expression of messenger RNA (mRNA) for interleukin-2, 3, 4, and 5, granulocytemacrophage colony-stimulating factor (GM-CSF), and interferon gamma by in situ hybridization with 32P-labeled complementary RNA. Localization of mRNA to BAL T cells was assessed by simultaneous in situ hybridization and immunofluorescence and by in situ hybridization after immunomagnetic enrichment or...
2,898 citations
TL;DR: In this paper, the type 2 cytokine IL-13, which shares a receptor component and signaling pathways with IL-4, was found to be necessary and sufficient for the expression of allergic asthma.
Abstract: The worldwide incidence, morbidity, and mortality of allergic asthma are increasing. The pathophysiological features of allergic asthma are thought to result from the aberrant expansion of CD4 + T cells producing the type 2 cytokines interleukin-4 (IL-4) and IL-5, although a necessary role for these cytokines in allergic asthma has not been demonstrable. The type 2 cytokine IL-13, which shares a receptor component and signaling pathways with IL-4, was found to be necessary and sufficient for the expression of allergic asthma. IL-13 induces the pathophysiological features of asthma in a manner that is independent of immunoglobulin E and eosinophils. Thus, IL-13 is critical to allergen-induced asthma but operates through mechanisms other than those that are classically implicated in allergic responses.
2,532 citations
TL;DR: Eosinophilic inflammation of the airways is correlated with the severity of asthma and these cells are likely to play a part in the epithelial damage seen in this disease.
Abstract: Background and Methods. The importance of eosinophils in the pathogenesis of bronchial asthma is not established. In an attempt to evaluate the role of eosinophilic inflammation in asthma, we compared 10 normal subjects with 43 patients with chronic asthma, 19 of whom had severe disease as assessed by a clinical scoring method described by Aas and by pulmonary-function tests. Eosinophils were counted in peripheral blood and bronchoalveolar-lavage fluid, and in biopsy specimens obtained from the patients and post mortem from 8 subjects without asthma, but not from the 10 normal controls. Eosinophil cationic protein was titrated by radioimmunoassay in the bronchoalveolar-lavage fluid from all subjects and studied by immunohistochemistry in the biopsy specimens. Results. There was a significant increase in the number of peripheral-blood eosinophils in the patients that was correlated with the clinical severity of asthma (P<0.001) and pulmonary function (P<0.03). Levels of eosinophils and eosinophil ...
2,526 citations
Journal Article•
TL;DR: In this article, the type 2 cytokine IL-13, which shares a receptor component and signaling pathways with IL-4, was found to be necessary and sufficient for the expression of allergic asthma.
Abstract: The worldwide incidence, morbidity, and mortality of allergic asthma are increasing. The pathophysiological features of allergic asthma are thought to result from the aberrant expansion of CD4 + T cells producing the type 2 cytokines interleukin-4 (IL-4) and IL-5, although a necessary role for these cytokines in allergic asthma has not been demonstrable. The type 2 cytokine IL-13, which shares a receptor component and signaling pathways with IL-4, was found to be necessary and sufficient for the expression of allergic asthma. IL-13 induces the pathophysiological features of asthma in a manner that is independent of immunoglobulin E and eosinophils. Thus, IL-13 is critical to allergen-induced asthma but operates through mechanisms other than those that are classically implicated in allergic responses.
2,429 citations
TL;DR: Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance the ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.
Abstract: Although asthma has been considered as a single disease for years, recent studies have increasingly focused on its heterogeneity. The characterization of this heterogeneity has promoted the concept that asthma consists of multiple phenotypes or consistent groupings of characteristics. Asthma phenotypes were initially focused on combinations of clinical characteristics, but they are now evolving to link biology to phenotype, often through a statistically based process. Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.
1,963 citations