Pathogenesis of rhinitis

Abstract

Summary:Rhinitis is a heterogeneous condition that has been associated with inflammatory responses as in allergic rhinitis but can also occur in the absence of inflammation such as in so-called 'idiopathic' (previously 'vasomotor') rhinitis. Allergic rhinitis affects approximately 1 in 4 of the population of westernised countries and is characterized by typical symptoms of nasal itching, sneezing, watery discharge and congestion. The intention of this review is to illustrate key concepts of the pathogenesis of rhinitis. Imbalance in innate and adaptive immunity together with environmental factors is likely to play major roles. In allergic rhinitis, initial allergen exposure and sensitization involves antigen presenting cells, T and B lymphocytes and results in the generation of allergen-specific T cells and allergen specific IgE antibodies. On re-exposure to relevant allergens crosslinking of IgE on mast cells results in the release of mediators of hypersensitivity such as histamine and immediate nasal symptoms. Within hours, there is an infiltration by inflammatory cells, particularly Th2 T lymphocytes, eosinophils and basophils into nasal mucosal tissue that results in the late-phase allergic response. Evidence for nasal priming and whether or not remodelling may be a feature of allergic rhinitis will be reviewed. The occurrence of so-called 'local' allergic rhinitis in the absence of systemic IgE will be discussed. Non-allergic (non-IgE mediated) rhinitis will be considered in the context of inflammatory and non-inflammatory disorders.Key words: Allergic rhinitis, non-allergic rhinitis, pathogenesis, priming, remodelling, Word count: 237. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Page 2 of 39 Clinical & Experimental Allergy Introduction:Rhinitis is a common heterogeneous chronic disorder in both children and adults that is defined as an inflammation of the nasal mucosa and characterised by the presence of one or more nasal symptoms that includes sneezing, itching, nasal discharge and nasal blockage.Allergic rhinitis is the most common form of non-infectious rhinitis that is associated with an IgE-mediated immune response against environmental allergens [1]. There are a number of rhinitis phenotypes that may be classified as shown in Table 1.The International Study of Asthma and Allergies in Childhood (ISAAC) revealed an increased worldwide trend of rhinitis with an average prevalence of 8-15% in children [2,3], with a prevalence in the general population ranging from 10-40% in industrialised countries [4][5][6][7]. Studies of the natural history of rhinitis in children have shown a prevalence of 2.8% and 11.8% at 4 years and 18 years of age for non-allergic rhinitis and, respectively, 3.4% and 27.3% for allergic rhinitis. The adjusted prevalence rate in adults was found to be 9.6% for non-allergic rhinitis and 29.8% for alle...

Evidence for the induction of Th2 inflammation by group 2 innate lymphoid cells in response to prostaglandin D2 and cysteinyl leukotrienes in allergic rhinitis

“…The most important allergens of seasonal AR are pollens, while those of perennial AR are house dust mites (HDMs): Dermatophagoides pteronyssinus and Dermatophagoides farinae . In sensitized individuals, inhaled antigens bind to IgE antibodies on mast cells and basophils, and chemical mediators such as histamine, prostaglandin D 2 (PGD 2 ) and cysteinyl leukotrienes (cysLTs) are released within minutes in early‐phase responses . These mediators stimulate sensory nerve endings and endothelial cells of blood vessels to cause sneezing, watery rhinorrhea and mucosal swelling .…”

“…In sensitized individuals, inhaled antigens bind to IgE antibodies on mast cells and basophils, and chemical mediators such as histamine, prostaglandin D 2 (PGD 2 ) and cysteinyl leukotrienes (cysLTs) are released within minutes in early‐phase responses . These mediators stimulate sensory nerve endings and endothelial cells of blood vessels to cause sneezing, watery rhinorrhea and mucosal swelling . Various inflammatory cells such as activated eosinophils infiltrate into the nasal mucosa in response to chemical mediators released during the early phase, leading to late‐phase responses at 4 to 12 hours after antigen exposure .…”

Human eosinophils and mast cells: Birds of a feather flock together

“…Allergic rhinitis, or hay fever, manifests as inflammatory conditions that affect the nasal mucosa, usually accompanied by sneezing, itching, watery discharge and/or blockage . Approximately 10‐40% of the population within industrialized countries, including 8‐15% of children, experiences these symptoms.…”

Association between Allergic Diseases and Irritable Bowel Syndrome: A Retrospective Study

“…The pathology of active wheals in patients with chronic urticaria (CU) has shown a large number of degranulated mast cells [8]. Relevant allergen exposure causes relief of inflammatory mediators of hypersensitivity through cross-link of immunoglobulin E (IgE) on mast cells in patients with AR [9]. In addition, increased mast cells in the duodenal and colonic mucosa have been found in patients with IBS [7].…”