Collection of Nasal Secretions and Tears and Their Use in Allergology

Sveva Castelli; Stefania Arasi; Ruby Pawankar; Paolo M. Matricardi

Disclosures

Curr Opin Allergy Clin Immunol. 2018;18(1):1-9. 

In This Article

Nasal Secretions in Patients with Allergic Rhinitis

Allergic Rhinitis is a very common IgE-mediated inflammatory disease caused by mucosal exposure to inhalant allergens.[17] The interaction of the inhaled allergen with the mastcell-bound IgE initiate a cascade of biochemical reactions, cellular activation, and recruitment of inflammatory mediators responsible for end organ response such as watery rhinorrhea.[18] Other characteristic symptoms include sneezing, nasal congestion, and itching.[19] The exploration of inflammatory cells and mediators in nasal secretions helps the understanding and monitoring of mucosal activity.[20] Specific secretory proteins and cellular activation markers may be used to measure the presence of inflammatory cells and their activity.[21] Eosinophil cationic protein (ECP) is a well standardized marker protein for the activity of eosinophilic nasal mucosal inflammation.[22,23] Myeloperoxydase (MPO) and Elastase has been used in many studies to reflect neutrophil activation.[24] Mast cell activity is marked notably by histamine, and by the more mast-cell–specific tryptase.[25] Cytokines play a dominant role in the pathophysiology of nasal diseases and can be determined in nasal secretions.[26]

Ig are the principle-specific mediators of host-defence in nasal secretions.[12] Immunoglobulin A (IgA) is the predominant immunoglobulin present on nasal mucosal surfaces, in which it acts as an active barrier against inhaled antigens and pathogens.[27] Secretory IgA (sIgA) is produced by plasma cells locally in the nasal mucosa and can be used as a marker of glandular secretions.[28] It takes part in the mucosal immunity of target organs of allergic diseases, such as the nasal airways.[29] Immunoglobulin G (IgG) is another major nasal protein that mediates specific antimicrobial functions.[30] It increases in secretions as a consequence of increased vascular permeability.[30] Different subclasses (IgG1–IgG4) have different roles in relation to the antigen.[31] IgG4 is associated with tolerance to aeroallergens, and is used as parameter of allergen immunotherapy monitoring.[32]

It is of great interest to measure IgE, key effector element in the allergic reaction, at the mucosal level. Local IgE production in nasal mucosa has been investigated with the analysis of nasal secretions since early years.[33] It was suggested that systemic IgE levels resulted from a surplus of the IgE produced locally in the nasal mucosa.[34] Evidence has been proved that the nasal mucosa is an active site for local somatic hypermutation, clonal expansion, and class switch recombination, crucial steps for the maturation of a B-cell into an IgE-secreting plasma-cell.[35–38] Measurements of local IgE may show high levels independently of serum IgE levels and atopic status.[39] Increased attention to the concept of a form of allergic rhinitis with local (nasal) but not systemic evidence of IgE sensitization[40–42] has raised the debate about the need of a new diagnostic algorithm, with a major role of antigen-specific IgE (sIgE) detection in nasal secretions.[5,43,44] IgE plays an important role also in other nasal diseases: increased levels of the antibody have been found in nasal polyposis.[45,46] The role of IgE detection in nasal secretions is gaining importance, thus it is still challenging because IgE is the least abundant Ig isotype, present at low concentrations in human fluids, in nanogram range.[47] Furthermore, several techniques are currently used for the collection of nasal secretions but there is no standardized method.[9]

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