Extraordinary stability of IgE-binding Parietaria pollen allergens in relation to chemically bound flavonoids.

It is known that the skin-active and IgE-binding components in Parietaria pollen extracts are not restricted to the predominant protein allergens of M(r) 12000-15000, but are present as well among the naturally occurring constituents of M(r) < 10000. Indeed, the IgE-binding Parietaria pollen components are quite heterogeneous, ranging from high- to low-molecular mass, whereby the IgE-binding epitopes display an unusual chemical stability. Furthermore, the pollen of Parietaria species demonstrably contain a high proportion of flavonoid pigments. Since these pollen grains cannot be collected entirely free from non-pollen plant parts, the usual allergenic extracts of Parietaria encompass both the polyphenolic substrate molecules and the enzyme polyphenoloxidase as ingredients for the oxidative generation of flavonol-protein conjugates during the extraction process. In the present work this is illustrated by spectroscopic analyses of the free and bound flavonoids in Parietaria pollen extracts, as well as of the peptide fragments produced from the allergenic proteins by enzymatic or chemical hydrolysis. None of these relatively harsh treatments had a significant effect on the IgE-binding properties of the allergenic (sub-)components, even though detectable proteins in isoelectric focusing and immunoblotting were lost. It is proposed that the extraordinary stability of IgE-binding Parietaria components over a wide molecular range may be attributed to chromophoric flavonoid side-chains as (parts of) the corresponding B-cell epitopes.

Comparative studies of allergenic extracts prepared from freshly collected, dried, or dried and defatted pollen.

Fresh pollen samples of Parietaria judaica, Betula pubescens, Dactylis glomerata and Olea europaea were collected and aliquot portions of these pollens were stored after drying in hot air, while other portions were dried and then defatted with diethylether. The different pollen materials were extracted with aqueous media to obtain the non-dialyzable allergenic protein constituents. Review of the production data, together with comparative analyses of the UV-absorption spectra and of IgE binding potencies did not reveal appreciable differences in allergen composition among extracts of fresh, dried, or dried and defatted pollen materials. However, microscopic examination showed the fresh pollen to be no longer viable.

Evaluation of the potency of allergenic extracts by inhibition of IgG-antibody binding.

A method is described for the in vitro potency evaluation of allergenic extracts by using their capacity of binding to specific human IgG antibodies. The results obtained with this inhibition-type enzyme immunoassay are compared with the analyses by the customary method of IgE antibody binding. A large series of allergenic protein fractions from the pollen of the Gramineae, Olea europea, Parietaria judaica, and from the dust mite Dermatophagoides pteronyssinus as well as from cat dander and peanuts were examined for inhibition of specific antibodies of both IgG and IgE isotypes. Potency evaluation by inhibition assays for IgE- and IgG-binding showed a significant correlation for the points of 50% inhibition (r = 0.92, p = 0.0001), but not for the slopes of the inhibition curves, i.e. the respective antibody avidities. Evidence is provided that the strict relationship between IgE- and IgG-inhibition by allergens could not be explained by possible cross-contaminations of the anti IgE- or anti IgG-reagents employed in the immunoassays. It is concluded that the inhibition of IgG-antibody binding presents a fast, reliable and low-cost alternative for the potency control of allergens used in clinical practice.

Pollen calendar of Seville and its relation to allergies.

We have carried out a study on the annual and weekly variation of airborne pollen in the air of Seville (Andalusia, Southern Spain) during 3 consecutive years using two Cour's collectors. We provide the pollen calendar of this city, which shows the annual distribution of the most important pollen types. Our results led us to check the validity of the pollen extracts usually used at the hospitals of the city to diagnose pollinosis.