Recognition of pollen and other particulate aeroantigens by immunoblot microscopy

Most grass-pollen types appear identical by normal light microscopy. Restricted antigenic cross-reactivity of Cynodon dactylon (Bermuda grass) pollen allowed development of a new method to identify antigens associated with grass-pollen grains. Pollen applied to the surface of an adhesive tape was blotted onto nitrocellulose, and the blots were identified by anti-Bermuda-grass antibodies, second antibody, and fluorescence microscopy. Of the 44 species of grass pollen studied for specificity of the method, the only species to demonstrate uniformly bright staining were Cynodon dactylon, Elymus triticoides, Elymus cinereus, and Koeleria cristata. Thirty-one species were negative, and nine other species demonstrated occasional brightly fluorescent spots, suggesting contamination. The immunoblotting method was used to study Tucson air collected continuously by a Burkard pollen and spore trap throughout April 1986. Each 2-hour transect of the adhesive tape from the trap was examined by immunoblotting and by normal light microscopy to compare antigen particle counts with grass-pollen counts. The mean antigen-particle concentration, 52.8/m3 of air, was higher than the mean grass-pollen concentration, 21.9/m3 of air, suggesting presence of amorphous Bermuda-grass antigens in air samples. Antigen-particle concentration, not grass-pollen concentration, correlated significantly with wind velocity, temperature, and time of day.