Demonstration of close physicochemical similarity and partial immunochemical identity between the major allergen, Dp42, of the house dust mite, D. pteronyssinus and corresponding antigens of D. farinae (Df6) and D. microceras (Dm6).

House dust mite antigens Df6 and Dm6, corresponding to Dermatophagoides pteronyssinus (Dp) antigen 42 (= P1), were purified from cultures of Dermatophagoides farinae (Df) and Dermatophagoides microceras (Dm) using hydrophobic interaction chromatography in combination with gel filtration or acetone precipitation. Purified antigens from the three mite species (Dp42, Df6 and Dm6) were similar regarding molecular weight by gel filtration (D. pteronyssinus: 17,000, D. farinae: 17,000 and D. microceras: 18,500) and by sodium dodecyl sulfate polyacrylamide gel electrophoresis (D. pteronyssinus: 30,000, D. farinae: 28,000 and D. microceras: 29,000). Widely spaced isoelectric points were observed for the antigens of all three species by sucrose gradient isoelectric focusing: (D. pteronyssinus: 4.5 and 6.3, D. farinae: 4.9 and 6.9 and D. microceras: 4.9 and 6.5). Species-specific rabbit antibodies were easily detected for all three species in crossed-line immunoelectrophoresis using mixtures of the two heterologous antigens in the intermediate gel. Antibody specificity for an epitope, common to D. farinae and D. microceras, but not shared by D. pteronyssinus, was further demonstrated. Potent rabbit antibody reagents with species specificity were produced by column immunoabsorption. Despite a probable common molecular structure and origin, the antigens of the three species exhibited gross differences in their immunochemical reactions with rabbit antibodies.