Clinical studies of a purified timothy pollen extract: desensitization therapy with a purified timothy pollen preparation compared to a crude timothy pollen extract. II. Results of the tests in vitro and their relation to symptoms and tests in vivo.

Perennial desensitization therapy was given during a period of 3.5 years to 40 children allergic to grass pollen allergens. 20 patients were treated with a crude and another 20 with a purified timothy pollen extract. 8 children served as untreated controls. The concentration of total and specific IgE in the treated groups covaried with those in the control group. Neither a suppression of the seasonal booster effect nor a suppression of IgE synthesis attributable to the treatment was found. The rise of timothy-specific "blocking' IgG antibodies was more pronounced in the group treated with the purified extract than in the group treated with the crude extract. A significant difference was found only after 3.5 years of treatment. The amplitude of rise of IgG antibodies correlated significantly with the effect of the treatment as judged by repeated conjunctival titration test. The results suggest that a good IgG response is an indication of successful therapy and that a better IgG response may be achieved with purified allergen extracts.