Abortive pollen germination: a mechanism of allergen release in birch, alder, and hazel revealed by immunogold electron microscopy.
BACKGROUND
Pollen from early-flowering trees (eg, birch, alder, hazel) represent major seasonal allergen sources. The effects of rain on the release of allergens from tree pollen has thus far not been studied at the ultrastructural level.


OBJECTIVE
This study was designed to investigate the effects of rain on the morphology of pollens from early-flowering trees and of potential rain-induced mechanisms of allergen release.


METHODS
Freshly collected pollen grains (birch, alder, and hazel) were exposed under controlled conditions to rainwater. Changes of pollen morphology and the release of allergens were analyzed by scanning electron microscopy. The release of allergen-bearing submicronic particles was studied by field emission scanning electron microscopy and transmission electron microscopy in conjunction with immunogold staining by using antibodies with specificity for the major allergens.


RESULTS
Scanning electron microscopy showed that freshly isolated pollen grains from birch, alder, and hazel have abortive germination in rainwater. Abortive pollen germination is characterized by the formation of short pollen tubes, which rupture at their tips and release micronic and submicronic particles containing major allergens. Immunogold transmission electron microscopy provided evidence that the allergens are transported through the pollen tubes during germination.


CONCLUSIONS
Rainwater-induced release of allergen-bearing submicronic particles from abortively germinated tree pollens may represent a mechanism of allergen release, with important implications on the induction of asthma as well as on current methods for measuring environmental allergen exposure.
Institute of Medical Physics and Biophysics, University of Münster, Germany.
Monika
M
Grote
Rudolf
R
Valenta
Rudolf
R
Reichelt
D000485:Allergens / Q000378:metabolism*; D029661:Alnus / Q000276:immunology*; D029662:Betula / Q000276:immunology*; D018525:Germination / Q000502:physiology*; D016253:Microscopy, Immunoelectron; D011058:Pollen / Q000254:growth & development* / Q000648:ultrastructure; D011891:Rain
D000485:Allergens