Cross-reactivity between antigens of fungal extracts studied by RAST inhibition and immunoblot technique.

We have used the RAST-inhibition technique in homologous and heterologous inhibitions of the Aspergillus fumigatus, Alternaria tenuis, and Cladosporium herbarum RAST assays followed by the immunoblot technique to assess the degree of shared allergenic determinants in these extracts. In the Aspergillus RAST, there was little or no inhibition with Cladosporium and Alternaria, but considerable cross-reactivity was found between Alternaria and Cladosporium. Inhibition by Alternaria of the Cladosporium RAST was found in a dose-dependent fashion in one serum, whereas all four sera in the Alternaria RAST were inhibited by Cladosporium in this fashion. Logit transformation of the Alternaria RAST-inhibition curves produced common slopes with Alternaria and Cladosporium in three of the four sera, indicating their immunologic identity. The immunoblot technique confirmed the degree of cross-reactivity found by RAST inhibition among the molds. This evidence of common allergenic determinants in these fungi could help to explain the observation that mold-allergic patients often have skin test reactions to several fungi.