Influence of aeroallergens on respiratory epithelial cells: a comparison of house dust mite and grass pollen allergens

Respiratory epithelial cells function as physical barrier and have shown to be active participants within the process of defense against pathogens and recognition of allergens. Upon activation they release inflammatory mediators thereby creating a micro environment in which recruited immunocompetent cells induce a local immune response. House dust mite (HDM) extract as a source of allergens has been shown to induce a broad panel of genes upon stimulation of epithelial cell line NCI-H292. The proteolytic activity of these HDM allergens has been proposed to be involved in the activation process.

The aim of this study was to compare the influence of HDM extract on respiratory epithelial cells with grass pollen allergen-induced activation of these cells with regard to the mechanism of activation, gene expression level, and the level of induced cytokine and chemokine release. In contrast to the HDM major allergen Der p 1, we were able to show that the major allergen of Phleum pratense, Phl p 1, although sharing molecular similarities with Der p 1, does not display any enzymatic activity under physiological conditions. Therefore, in this study respiratory epithelial cells were stimulated with grass pollen extract and purified Phl p 1. Chemokine and cytokine release was determined by multiplex enzyme-linked immunosorbent assay and mRNA was used for cDNA-microarray analysis. First data show that both, HDM extract and grass pollen allergens, induce the release of IL-6 and IL-8 from NCI-H292 cells. Furthermore, stimulation with HDM extract leads to the release of TNF-α, GM-CSF and IFN-γ. Interestingly none of these mediators was induced after stimulation with grass pollen extract or purified Phl p 1. In contrast to HDM extract grass pollen allergens induce the release of MCP-1 from respiratory epithelial cells, as well as moderate levels of IL-12. Detailed characterization of the response on gene expression level might give new insights into the pathophysiology of grass pollen allergy and a comparison with HDM induced expression profiles will be helpful towards understanding the allergic response in general.