Specific IgE response toward allergenic molecules during perennial hyposensitization: a three-year prospective double-blind study.

Allergenic extracts are multicomponent systems containing a number of potentially allergenic molecules. In a 3 yr prospective double-blind study, sera from 40 patients hyposensitized with either a two-component timothy extract or a 20-component timothy extract were evaluated by means of crossed radioimmunoelectrophoresis. The patients exhibited specific IgE response toward individual allergenic molecules, and IgE with new specificities did not develop after hyposensitization. A high degree of clinical protection could generally be obtained on treatment with the 20-component timothy extract, but this was true only with the two-component timothy extract containing the allergenic molecules that matched the individual IgE response.