Researchers from Bochum have isolated the substance in cowshed dust that possibly protects farm children from developing allergies and allergic asthma -- namely the plant sugar molecule arabinogalactan. If high concentrations are inhaled during the first year of life, it inhibits the immune system from excessive defense reactions.
There are large quantities of this molecule in forage crops such as the Meadow Foxtail (Alopecurus pratensis). The researchers from Bochum, Munich and Borstel, working the under the auspices of Dr. Marcus Peters (Department of Experimental Pneumology at the RUB, Prof. Dr. Albrecht Bufe), were able to demonstrate experimentally that the molecule affects immune system cells.
They report their findings in the current edition of the Journal of Allergy and Clinical Immunology.
The needle in the haystack
It has long been know that children who grow up on farms are less prone to allergies and allergic asthma. However, just what it is that protects them remained a riddle for a long time. Dr. Marcus Peters stated that finding the protective substance was like looking for the proverbial needle in the haystack. He could make use of stable dust collected from diverse farms in Germany, Austria, and Switzerland, an analysis of which disclosed that it is primarily comprised of plant substances. Over ten percent thereof is arabinogalactan, a large sugar molecule, thus it was classified as "suspicious."
Prevent excessive alertness of the immune system
The researchers thus tested the reaction of the immune system of mice to potential allergens if arabinogalactan molecules are present. Dr. Peters stated that they found that the dendritic cells, which introduce damaging invaders to the immune cells and cause them to react, change their behaviour if arabinogalactan is present. They then produce a specific transmitter that suppresses the immune reaction. It remains to be clarified which receptors of the dendritic cells are responsible for this mechanism.
Sugar receptors are generally important for the immune system to help it to identify foreign particles. Dr. Peters explained that this suppression of the immune system was not new to them. Some bacteria also make targeted use of this mechanism to reduce the immunoreaction of the host. Arabinogalactan does however only prevent the excessive alertness of the immune system -- the resistance to pathogenic agents continues to function normally.
It depends on the dose
The researchers were not surprised that a grass component -- of all things -- protects children against hay fever. Dr. Marcus Peters stated that it is all a question of the concentration. Low concentrations of Meadow Foxtail pollen can lead to allergies, whereas high doses in the very early stages of life can also prevent them. After all, hyposensitization is also based on the principle of increasing the dose. The scientists now plan to investigate whether arabinogalactan can be used as prophylaxis or whether it is also suitable for the treatment of allergies and allergic asthma. It is conceivable that arabinogalactan could be used as spray or nose drops because it is highly water-soluble.
- Marcus Peters, Marion Kauth, Olaf Scherner, Kirsten Gehlhar, Imke Steffen, Pia Wentker, Erika von Mutius, Otto Holst, Albrecht Bufe. Arabinogalactan isolated from cowshed dust extract protects mice from allergic airway inflammation and sensitization. The Journal of Allergy and Clinical Immunology, 2010; DOI: 10.1016/j.jaci.2010.05.011
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