Dear Dr Wise,
The explanation of the allergenicity in anemophilous pollen as you cite it
in your question to the plant-ed group, was popular some years ago. Lately,
quite a few allergens have been identified and are known as to the
molecular structure, and it appears as they may have several biological
functions apart from recognition at pollination, such as host-pathogen
interaction, Ca2+binding and cell wall-loosening activities. One
"pan-allergen", cause of pollinosis as well as food allergies provoked by
several plant species, is the ubiquitous actin-binding protein profilin.
The main reason for the fact that anemophilous pollen are overrepresented
as causes of allergy (which is true), as compared to entemophilous, is that
people in general are much more exposed to it. The maximum concentration of
birch pollen this spring in West Sweden was 5000 grains per cubic metre of
air! Entomophilous pollen grains remain in the flower until fetched by the
insect, and thus less often enter the human nose. They do not as a rule
contain less allergens and some of them may be causes of "occupational"
allergies, e.g., in florists. In some entomophilous species with exposed
anthers, such as in oilseed rape, pollen grains are often released into the
air. Rape pollen sometimes causes allergy in the proximity of fields where
these plants are cultivated (the main allergen in Brassica is shown to be
similar to one in birch).
Of course, there are also several anemophilous species who are not known to
provoke allergy; other factors are also important, such as molecular
structure and the speed of release from the pollen. Thus: the allergen
content per se is not correlated to pollination system, but the degree of
human exposure is.
You may be interested in the following references, where the possible
biological functions of pollen allergens are discussed. Other references
could be delivered on request.
Stewart, G. A. & Thompson, P. J. 1996. The biochemistry of common
aeroallergens. Clin. Exp. Allergy, 26: 1020-1044
Mohapatra, S. S. & Knox, R. D. (eds.) 1996: Pollen: biotechnology, gene
expression and allergen characterization, pp.. Chapman & Hall, London and
New York.
Best wishes,
Åslög Dahl (head of the pollen information service in South Sweden).
Dr. Åslög Dahl
PollenGruppen i Göteborg AB organisation no. 556522-6155
Department of Botany Tel: +46 31 773 2664
Box 461 Fax: +46 31 773
2677
S-405 30 Göteborg, Sweden email:aslog.dahl at systbot.gu.se
homepage: http://www.systbot.gu.se/staff/asldah/welcome.html
