Birch-pollen antigenic activity of settled dust in rural and urban homes.

Concentrations of birch-pollen antigens were measured in 10 homes in southwestern Finland, four in urban and six in rural areas. Dust samples were collected once a week with a vacuum cleaner equipped with a special collection device (ALK, Copenhagen) combined with an exchangeable glass microfiber filter in a filter dish. Control samples were taken from horizontal surfaces outdoors. All samples were analyzed by a modification of the IgG-ELISA procedure. The birch-pollen antigenic activity in indoor settled dust was lower than that in dust outdoors. The mean concentration of antigenic activity indoors peaked 3 weeks later than outdoors. The lag indicates that the most important means whereby antigens are carried indoors is via footwear and clothes, rather than, for instance, ventilation. Antigenic activity was still detected 2 months after the peak pollen period. As a source of antigens, both indoor and outdoor dust may be an important cause of pollen-allergy symptoms after the season.

Comparison of direct immunostaining and electroimmunoassay for analysis of airborne grass-pollen antigens.

Sensitive pollen-allergic patients have been reported to show allergic symptoms not only during the pollen release of allergenic plants but also both before and after the pollen season. Symptoms before the season are evidently provoked by small-sized particles originating partly from developing pollen grains, partly from other plant parts. After the pollen season, antigenic material settles on various surfaces, which thus form a new source of allergenic material. Measuring the allergen concentrations in indoor and outdoor environments demands an effective sampling method and a rapid and sensitive immunochemical analysis, especially for particles of small-sized fractions which are not detected in microscopic analyses. The efficiency of an ELISA and an immunochemical staining method was tested with monoclonal IgG against Phl p 5, the main grass allergen. The Burkard trap and MPC impactor (Marple personal cascade impactor with six-stage particle size fractionation) were compared. The sampling was carried out in southwestern Finland in the summer of 1994. The number of grass-pollen antigen spots greatly exceeded the simultaneous pollen count, indicating considerable antigen activity outside the pollen grains. The counts were especially high in small-sized fractions after the pollen season, when hardly any airborne pollen was found. Spots and pollen divided according to size were highly intercorrelated, indicating that the threshold values used were appropriate.