MEASUREMENT OF ALLERGEN-SPECIFIC IGD AND CORRELATION WITH ALLERGEN-SPECIFIC IGE

A new method for the measurement of allergen-specific IgD (as-IgD) was developed by modifying the ImmunoCAP assay (Pharmacia), and amplifica tion of the signal with a goat anti-human/rabbit anti-goat detection s ystem. The assay was sensitive enough to measure as-IgD in serum sampl es. The specificity of the assay was examined using inhibition tests w ith excess corresponding and noncorresponding allergens. For the diffe rent allergens inhibition rates between 56% (house dust mite) and 88% (cat) could be achieved. Non-corresponding allergens did not inhibit t he as-IgD binding. Total IgE and allergen-specific IgE (as-IgE) was me asured using the ImmunoCAP system. Total IgD was measured using a sand wich ELISA. As-IgD was measured in serum samples from 51 atopic and 23 nonatopic subjects, and the correlation with as-IgE was examined. As- IgD was detected in both atopics and non-atopics but at higher levels in atopics. As-IgD against birch pollen and timothy pollen allergen wa s found to be increased in atopics with IgE directed against these all ergens compared to atopics without IgE against these allergens (P < 0. 02 and P < 0.03). As-IgD against birch pollen allergen was higher in a topics with IgE specific to this allergen than in non-atopics (P < 0.0 2). In contrast to total IgE and total IgD, significant correlations w ere observed between as-IgD and as-IgE against timothy pollen (r = 0.3 4, P < 0.04), birch pollen (r = 0.38, P < 0.05) and cat dander allerge n (r = 0.52, P < 0.01). The observed correlations between as-IgD and I gE suggest that IgD and IgE may be similarly regulated, and thus the m easurement of as-IgD may give further insight into the regulation of I gE.