Histamine release from isolated mast cells as a bioassay system for the standardization of allergens

Standardization of allergen extracts is still a problems not yet satisfactorily resolved. Allergic sensitization involves not only the production of allergen-specific antibodies of a certain class (IgE) but also changes in the morphological and functional state of the mast cells that bind and carry IgE and react with the allergen. We therefore designed a bioassay which covers the total allergenicity and also antibody-independent allergen effects. It is based on the release of histamine from isolated mast cells of actively sensitized guinea pigs: outbred animals receive one s.c. injection of the allergen extract to be tested and human serum albumin (HSA) as reference (standard) allergen. Three weeks later the mesenteric mast cells of these animals are isolated and challenged in vitro with varying concentrations of the test allergen and HSA. The relationship of the histamine release caused by the reference allergen HSA to that caused by the test allergen (e.g. rye or grass pollen, alternaria, and even house dust) can be used to estimate the sensitizing and challenging potency of the test allergen. For example, 2 different batches of rye pollen gave different results although the values obtained by identical batches were almost identical within 9 months. In addition, irritating impurities of the allergen extract might be recognized.