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Two purified allergens, designated as DF1 and DF2, were isolated from the extract of the whole culture of Dermatophagoides farinae by a combination of ammonium sulfate precipitation and ion exchange, hydrophobic, chelate and gel chromatography. DF1 was isolated as a heat-sensitive acidic protein with an apparent molecular weight of 25,000 and an isoelectric point of 4.6–7.2. DF2 was isolated as a heat-stable basic protein with an apparent molecular weight of 15,000 and an isoelectric point of 7.8–8.3. No allergenic cross-reactivity was seen between DF1 and DF2. Both DF1 and DF2 were shown to be the major allergens of D. farinae by the results of radioallergosorbent test and histamine release assay.

Two major allergens, DPI (Der p I) and DP2 (Der p II), were isolated from the whole culture extract of Dermatophagoides pteronyssinus, and the physicochemical and immunochemical properties of these allergens were compared with those of the corresponding allergens from Dermatophagoides farinae, DF1 (Der f I)and DF2 (Der f II).On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polyacrylamide gel isoelectric focusing and amino acid analysis, both DP1 and DP2 were demonstrated to have close physicochemical similarity with DF1 and DF2, respectively. On immunodiffusion with the use of rabbit antisera, the two Der I allergens showed the reaction of typical partial identity, while the two Der II allergens showed the reaction of almost complete identity. Radioallergosorbent test (RAST) and RAST absorption experiments with the use of sera from mite-allergic patients showed that human IgE antibody response to the Der I allergens was directed against both cross-reactive and species-specific determinants. In contrast, IgE antibodies to the Der II allergens were demonstrated to react almost completely to cross-reactive determinants.

Human eosinophils and neutrophils were isolated from 20 ml of peripheral blood by dextran sedimentation, centrifugation with lymphoprep, and density gradient centrifugation with Percoil. The incubation of neutrophils of purity higher than 99% (density: 1.080–1.085 g/ml) with calcium ionophore A23187 for 20 min resulted in the release of a little amount of leukotriene C₄ (2.3 ± 0.6 ng/10⁶ cells) as measured with a commercial radioimmunoassay kit. On the other hand, the release from eosinophils was over 10 times that from neutrophils. When the releasability of leukotriene C₄ from eosinophils was examined in relation to the cell density, the eosinophils with lower density were observed to produce greater amounts of leukotriene C₄.

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