Solid-phase radioimmunoassay for the measurement of IgG antibodies specific for the house dust mite, Dermatophagoides farinae.

The sera from 65 asthmatic patients were studied for the measurement of IgG antibodies specific to the house dust mite, Dermatophagoides farinae (D. farinae) by solid-phase radioimmunoassay using polystyrene tubes coated with the antigen extract. The solid-phase radioimmunoassay had about the same sensitivity as the conventional double antibody antigen-binding assay in the detection of mite-specific IgG antibodies. The mean value of IgG antibodies was 26.1 (+/- 39.8) micrograms/ml in patients hyposensitized with D. farinae, 23.9 (+/- 29.3) micrograms/ml in those hyposensitized with house dust (HD), and 21.6 (+/- 35.6) micrograms/ml in non-treated patients. A significant difference was detected between HD-treated patients and normals (p less than 0.05). The levels of IgG antibody tended to increase with the increment of the maintenance dose of the D. farinae or HD used in immunotherapy. In addition, eight patients were evaluated for their IgG antibody levels before and after immunotherapy. In five of them, IgG antibodies increased about two to threefold above the value before immunotherapy. These results suggest that the measurement of IgG antibodies by solid-phase radioimmunoassay may be clinically useful in evaluating the effectiveness of immunotherapy.