Phleum pratense pollen starch granules induce humoral and cell-mediated immune responses in a rat model of allergy

• Published in: Clinical and experimental allergy 2004-02, Vol.34 (2), p.310-314
• Main Authors: Motta, A., Peltre, G., Dormans, J. A. M. A., Withagen, C. E. T., Lacroix, G., Bois, F., Steerenberg, P. A.
• Format: Article
• Language: English
• Subjects: Allergens - immunology; Allergic diseases; allergy; Animals; asthma; Biological and medical sciences; Bronchi - immunology; Environmental Sciences; Fundamental and applied biological sciences. Psychology; Fundamental immunology; Hypersensitivity - immunology; Immunoglobulin E - blood; Immunologic Tests; Immunopathology; Life Sciences; Lymph Nodes - immunology; Medical sciences; Microscopy, Electron, Scanning; Phleum - immunology; Phleum pratense; Pollen - ultrastructure; Rats; Rats, Inbred BN; Starch - immunology; Starch - isolation & purification; starch granules; timothy grass pollen; Toxicology
• ISSN: 0954-7894; 1365-2222
• DOI: 10.1111/j.1365-2222.2004.01872.x

Summary Background Timothy grass (Phleum pratense) pollen allergens are an important cause of allergic symptoms. However, pollen grains are too large to penetrate the deeper airways. Grass pollen is known to release allergen‐bearing starch granules (SG) upon contact with water. These granules can create an inhalable allergenic aerosol capable of triggering an early asthmatic response and are implicated in thunderstorm‐associated asthma. Objective We studied the humoral (IgE) and bronchial lymph node cells reactivities to SG from timothy grass pollen in pollen‐sensitized rats. Methods Brown–Norway rats were sensitized (day 0) and challenged (day 21) intratracheally with intact pollen and kept immunized by pollen intranasal instillation by 4 weeks intervals during 3 months. Blood and bronchial lymph nodes were collected 7 days after the last intranasal challenge. SG were purified from fresh timothy grass pollen using 5 μm mesh filters. To determine the humoral response (IgE) to SG, we developed an original ELISA inhibition test, based on competition between pollen allergens and purified SG. The cell‐mediated response to SG in the bronchial lymph node cells was determined by measuring the uptake of [3H]thymidine in a proliferation assay. Results An antibody response to SG was induced, and purified SG were able to inhibit the IgE ELISA absorbance by 45%. Pollen extract and intact pollen gave inhibitions of 55% and 52%, respectively. A cell‐mediated response was also found, as pollen extract, intact pollen and SG triggered proliferation of bronchial lymph node cells. Conclusions It was confirmed that timothy grass pollen contains allergen‐loaded SG, which are released upon contact with water. These granules were shown to be recognized by pollen‐sensitized rats sera and to trigger lymph node cell proliferation in these rats. These data provide new arguments supporting the implication of grass pollen SG in allergic asthma.