Abstract
BackgroundAllergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or even high humidity. Because of their size SPP can preferentially reach the lower airways where they come into contact with surfactant protein (SP)-D. Our previous work demonstrated that SP-D increases the uptake of SPP by alveolar macrophages. In the present study, we investigated the uptake of SPP in human primary epithelial cells and the potential modulation by SP-D. The patho-physiological consequence was evaluated by measurement of pro-inflammatory mediators.MethodsSPP were isolated from timothy grass and subsequently fluorescently labelled. Human primary bronchial epithelial cells were incubated with SPP or polystyrene particles (PP) in the presence and absence of surfactant protein D. In addition, different sizes and surface charges of the PP were studied. Particle uptake was evaluated by flow cytometry and confocal microscopy. Soluble mediators were measured by enzyme linked immunosorbent assay or bead array.ResultsSPP were taken up by primary epithelial cells in a dose dependent manner. This uptake was coincided with secretion of Interleukin (IL)-8. SP-D increased the fraction of bronchial epithelial cells that bound SPP but not the fraction of cells that internalized SPP. SPP-induced secretion of IL-8 was further increased by SP-D. PP were bound and internalized by epithelial cells but this was not modulated by SP-D.ConclusionsEpithelial cells bind and internalize SPP and PP which leads to increased IL-8 secretion. SP-D promotes attachment of SPP to epithelial cells and may thus be involved in the inflammatory response to inhaled allergen.
Highlights
Allergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or even high humidity
The percentage of commercially available Normal human bronchial epithelial cells (NHBE) which took up SPP or had attached SPP, investigated by flow cytometry, followed a dose-response relationship (Figure 3A)
Eight hours of incubation with 5 × 106 SPP/cm2 led to 8.7 ± 2.3% positive NHBE
Summary
Allergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or even high humidity. Because of their size SPP can preferentially reach the lower airways where they come into contact with surfactant protein (SP)-D. Allergen-containing subpollen particles (SPP) are released from whole plant pollen upon contact with water or in the presence of high humidity [1] This release occurs regularly in our environment and it is associated with an increased occurrence of asthma-symptoms during thunderstorms [1]. The interaction of SPP, isolated from timothy grass, with human primary bronchial epithelial cells and its modulation by surfactant protein D was investigated. In order to study the influence of size and surface charge on particle binding and uptake, experiments with various polystyrene particles of different size and surface charge were performed
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