Studies on Alternaria Allergens

Abstract

The biochemical and immunological characteristics of a series of commercial samples of <i>Alternaria tenuis</i> were examined, including samples from two different companies. There was a considerable variation in the biochemical parameters such as the gel filtration profile on Sephadex G-100, isoelectric focussing pattern and immunodiffusion precipitin band pattern. The content and proportion of two high molecular weight polysaccharides, one a galactomannan and the other a glucan, also varied greatly. In contrast, the allergenic properties of the samples were more consistent. In rat IgE passive cutaneous anaphylaxis tests, extensive cross-reactivity was observed among batches from the same company, but this cross-reactivity was weaker when batches from the two companies were compared. In direct radioallergosorbent tests (RAST) the samples showed similar reactivities, but RAST inhibition tests showed a 40-fold range in activity between samples from one company and 55-fold between batches from the two sources. It was found that the proportions of the major <i>A. tenuis</i> allergen and a related hypoallergenic antigen in the samples were relatively constant, hence RAST inhibition can be used as a measure of allergenic potency despite the presence of this cross-reacting antigen. The lack of correlation between allergenic and biochemical properties of the various samples suggests that a simple biochemical test is unlikely to be a satisfactory replacement for the RAST inhibition assay in standardizing <i>A. tenuis</i> extracts.