Determination of the allergenic activity of birch pollen and apple prick test solutions by measurement of β‐hexosaminidase release from RBL‐2H3 cells. Comparison with classical methods in allergen standardization

Background: A murine in vitro model of the allergic type I reaction was set up to determine the biologic activity of extracts without involvement of human beings. It is based on β‐hexosaminidase release from passively sensitized RBL cells after allergen challenge. The intended application of this RBL cell assay in the field of quality control of allergenic extracts requires its comparison with established methods. Methods: The activity of five standardized birch‐pollen prick test solutions was determined in parallel by RBL assay, direct IgE binding, IgE‐binding inhibition, major allergen content, histamine‐release assay, and skin testing. Results: The RBL cell‐release assay corresponded well to other methods if a reagin raised against natural birch‐pollen extract was used for passive sensitization. However, in the case of a reagin against recombinant Bet v 1, only a decreased activity was observed, presumably because a reduced number of epitopes were recognized by the monospecific reagin. In contrast to standardized birch‐pollen extracts, nonstandardized apple extracts showed poor activity in all assays. Conclusions: This murine model might be a useful tool in the quality control of allergenic extracts. It combines properties of assays based on standardized antisera and of assays that consider IgE cross‐linking properties.