title: Linking surfactant protein SP-D and IL-13: implications in asthma and allergy.
abstract: Surfactant protein D (SP-D) is an innate immune molecule that plays a protective role against lung infection, allergy, asthma and inflammation. In vivo experiments with murine models have shown that SP-D can protect against allergic challenge via a range of mechanisms including inhibition of allergen-IgE interaction, histamine release by sensitised mast cells, downregulation of specific IgE production, suppression of pulmonary and peripheral eosinophilia, inhibition of mechanisms that cause airway remodelling, and induction of apoptosis in sensitised eosinophils. SP-D can also shift helper T cell polarisation following in vivo allergenic challenge, from pathogenic Th2 to a protective Th1 cytokine response. Interestingly, SP-D gene deficient (-/-) mice show an IL-13 over-expressing phenotype. IL-13 has been shown to be involved in the development of asthma. Transgenic mice over-expressing IL-13 in the lung develop several characteristics of asthma such as pulmonary eosinophilia, airway epithelial hyperplasia, mucus cell metaplasia, sub-epithelial fibrosis, charcot-Leyden-Like crystals, airways obstruction, and non-specific airways hyper-responsiveness to cholinergic stimulation. Although both IL-4 and IL-13 are capable of inducing asthma like phenotype, the effector activity of IL-13 appears to be greater than that of IL-4. SP-D -/- mice seem to express considerably higher levels of IL-13, which is consistent with increased sensitivity and exaggerated immune response of the mice to allergenic challenge. Allergenic exposure also induces elevation in SP-D protein levels in an IL-4/IL-13-dependent manner, which prevents further activation of sensitised T cells. This negative feedback loop seems essential in protecting the airways from inflammatory damage after allergen inhalation. Here, we examine this link between IL-13 and SP-D, and its implications in the progression/regulation of asthma and allergy.
authors.affiliation: Centre for Infection, Immunity and Disease Mechanisms, School of Health Sciences and Social Care, Brunel University, London, UK.
authors.forename: Asif S
authors.initials: AS
authors.lastname: Qaseem
authors.forename: Sanchaita
authors.initials: S
authors.lastname: Sonar
authors.forename: Lakshna
authors.initials: L
authors.lastname: Mahajan
authors.forename: Taruna
authors.initials: T
authors.lastname: Madan
authors.forename: Grith L
authors.initials: GL
authors.lastname: Sorensen
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Shamji
authors.forename: Uday
authors.initials: U
authors.lastname: Kishore
mesh_terms: D000818:Animals; D001249:Asthma / Q000235:genetics* / Q000276:immunology; D004804:Eosinophils / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000235:genetics* / Q000276:immunology; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D018793:Interleukin-13 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008954:Models, Biological; D037663:Pulmonary Surfactant-Associated Protein D / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D018793:Interleukin-13; D037663:Pulmonary Surfactant-Associated Protein D