Immunochemical and physicochemical characterization of commercial Alternaria extracts: a model for standardization of mold allergen extracts.

To develop a model for mold allergen extract standardization, we studied eight commercial Alternaria extracts from various suppliers by a variety of immunochemical and physicochemical techniques, including measurement of Alt-I, a purified allergenic fraction of Alternaria. Wide variations were noted in the allergenic and antigenic potencies of these extracts. Estimates of Alt-I content measured by Alt-I RAST inhibition and by radioimmunoassay correlated significantly (p less than 0.05), but Alt-I activity by either method could not be correlated with allergenic potency as measured by RAST inhibiton using solid-phase Alternaria. Each test extract produced unique and differing patterns of Coomassie blue-stained bands in isoelectrofocusing gels and in crossed immunoelectrophoresis gels using rabbit antibodies to Alternaria. The optimal method for mold allergen standardization involves a combination of RAST inhibiton, isoelectrofocusing, and crossed immunoelectrophoresis techniques, and, if possible, quantitation of individual allergens.