Complement inactivation by allergenic plant pollen extracts.
Dialyzed aqueous extracts of plant pollen are widely used in the clinical practice of allergy for diagnostic and therapeutic purposes. The present investigation shows that such allergenic extracts are capable of consuming complement in every human serum, independent of the clinical condition. Complement is engaged by way of the first component C1, but without the participation of allergen-specific antibodies. The capacity of distinct pollen extracts to inactivate haemolytic complement was found to depend on the plant species, the most potent extracts being from the pollen of the weeds and trees. Analysis by UV-spectroscopy of the flavonoids remaining firmly bound to the proteins gives rise to the proposal that complement inactivation by allergenic and non-allergenic pollen extracts is due to polyphenolic (flavonoid) structures complexed with, or chemically conjugated to, the pollen proteins.