IgE‐bearing Cells in Bronchoalveolar Lavage Fluid and Allergen‐specific IgE Levels in Sera from RAO‐affected Horses

Abstract

Recurrent airway obstruction (RAO) is a common condition in stabled horses characterized by small airway inflammation, airway neutrophilia and obstruction following exposure of susceptible horses to mouldy hay and straw and is thus regarded as a hypersensitivity reaction to mould spores. However, the role of immunoglobulin E antibodies (IgE) in the pathogenesis of RAO is unclear. We hypothesized that the number of cells with receptor-bound IgE in bronchoalveolar lavage fluid (BALF) and IgE levels in serum would be higher in RAO-affected than in healthy horses living in the same environment. Therefore, IgE-positive (+) cells were identified by immunocytochemistry on cytospins from BALF and counted. IgE levels against the mould extracts Aspergillus fumigatus (Asp. f.) and Alternaria alternata (Alt. a.) and the recombinant mould allergen Aspergillus fumigatus 8 (rAsp f 8) were measured by enzyme-linked immunosorbent assay (ELISA) in the sera of seven RAO-affected and 22 clinically healthy mature horses housed in the same conventional stable environment. After correcting for the number of neutrophils, there were no significant differences in IgE+ cells on cytospins from BALF between both groups of horses (5% versus 7%, P > 0.1). Serum IgE levels against the mould extracts were significantly higher in RAO-affected than in clinically healthy horses [median = 119 versus 66 relative ELISA units (REU), P < 0.05]. Furthermore, significantly more RAO-affected than healthy horses had detectable serum IgE against the recombinant allergen rAsp f 8 (4/7 and 3/22, respectively, P < 0.05). Age had no significant effect on BALF cell ratios or on specific serum IgE levels. These results show that high IgE levels against mould antigens are associated with RAO under controlled environmental conditions but ranges of mould-specific serum IgE levels overlapped too much between diseased and clinically healthy animals to be of any diagnostic value. Further studies are needed to assess whether IgE-mediated reactions contribute to the pathogenesis of RAO.

Cytological evaluation of tracheal aspirate and broncho-alveolar lavage fluid in comparison to endoscopic assessment of lower airways in horses with recurrent airways obstruction or inflammatory airway disease

“…As it is difficult to establish a reliable proportion of mast cells in tracheal aspirates and in broncho-alveolar lavage fluid using the MCG stain method (Hansen 2014), and there is marked influx of these cells into the bronchial wall (Kunzle et al 2007), the number of the cells was not included in the study, but there was a higher percentage of mast cells in IAD horses when compared to RAO horses. A similar cell count determination, without a mast cell population, was done by Zang et al (2012).…”

Air Pollution and Domestic Animals

“…The role of IgE-mediated events in RAO is still puzzling. Serum IgE levels against fungal spores in RAO horses were significantly higher than in healthy horses, but counts of IgE receptor-bearing cell in BALF were not significantly different between healthy and RAO affected horses (Kunzle et al, 2007). Lavoie et al (2001) and Kim et al (2003) held a T-helper cell response of type 2 responsible for the clinical signs, similar to human allergic asthma.…”

Recurrent airway obstruction in horses - an allergic inflammation: a review

“…The same author argued that RAO-affected horses display chronic inflammatory disease with some indications for the involvement of a delayed-type hypersensitivity mechanism. But, as mentioned previously, several studies have investigated the role of IgE antibodies in the pathogenesis of RAO (Halliwell et al, 1993;Schmallenbach et al, 1998;Eder et al, 2000Eder et al, , 2001Curik et al, 2003;Kunzle et al, 2007;Moran et al, 2010a,b). These investigations suggest that IgE antibodies, which mediate immediate hypersensitivity, could be involved in the immunological mechanism leading to RAO.…”

“…In general, airway inflammation involves the activation of pathogenic-specific inflammatory cells, modulation of transcription factors and release of inflammatory mediators (Barnes, 1998). Type I hypersensitivity, which is IgE-mediated (Halliwell et al, 1993;Schmallenbach et al, 1998;Eder et al, 2000Eder et al, , 2001Curik et al, 2003;Kunzle et al, 2007;Tahon et al, 2009;Moran et al, 2010a,b), and type III hypersensitivity reactions have been suggested to play a role in airway inflammation (Franchini et al, 2000;Lavoie et al, 2001;. Studies suggest that RAO-affected horses have higher IgE levels against Faenia rectivirgula and Aspergillus fumigatus extracts in BALF (bronchoalveolar lavage fluid) than healthy controls (Halliwell et al, 1993;Schmallenbach et al, 1998).…”