Immunotherapy with cat- and dog-dander extracts. II. In vivo and in vitro immunologic effects observed in a 1-year double-blind placebo study

The effects of immunotherapy on the skin prick test, allergen-specific IgE, and IgG in 39 patients (19 adults and 20 children), treated with partially purified cat- or dog-dander extracts or placebo for 1 year, were studied by use of a double-blind protocol. IgG levels were measured by three different assays: IgG RAST, IgG4 RAST, and Staph A IgG1, 2, and 4. The skin prick test reaction decreased continuously in the allergen-treated patients, the decrease being the first sign of an immunologic effect of the therapy. Allergen-specific IgE levels increased during the first 9 months in both children and adults. The RAST activity during the last 3 months continued to rise for the children, whereas it declined for the adults. IgG levels measured by all three methods demonstrated an increase in the allergen-treated patients and no increase in the placebo-treated patients. The children developed higher values on IgG RAST and IgG4 RAST than the adults. IgG RAST correlated negatively with IgE levels in the cat allergen-treated group. No correlation between skin prick test results, IgE levels, and IgG levels was found, nor was there any correlation between these parameters and the patients' own subjective evaluation or the allergen bronchial challenge test. In summary, the expected change in skin prick test reaction and allergen-specific IgE and IgG levels was found. The children tended to be more immunologically active than the adults.