Immunotherapy with cat- and dog-dander extracts: IV. Effects of 2 years of treatment

Abstract

Thirty-five patients (20 children and 15 adults) with animal-dander asthma completed 2 years of immunotherapy with partly purified and standardized cat- or dog-danger extracts. The first year of the study was performed double-blind with a placebo-treated control group. These 15 patients were transferred to active treatment for a second year. All patients were followed by use of the skin prick test (SPT), allergen and histamine bronchial challenges, and tests for allergen-specific IgE, IgG1, and IgG4 levels. In the group treated with active extracts for 2 years (group A), the previously reported decrease in bronchial responsiveness to cat extract ( p < 0.001) and histamine ( p < 0.01) was even more pronounced after the second year. After 1 year of active treatment in the original placebo group (group B), a significant decrease in the bronchial responsiveness to cat extract was noted ( p < 0.001). The responsiveness to histamine was decreased only in the patients treated with cat-dander extracts ( p < 0.05). A significant decrease in the SPT ( p < 0.001) and an increase in the allergen-specific IgE ( p < 0.001) and IgG4 ( p < 0.001) was also noted in patients (group B) treated with cat-dander extracts. The side effects in the two groups (A and B) were negligible, except for some systemic side effects, especially among the children during the initial phase of immunotherapy. The symptoms were mild and responded promptly to treatment. The fact that the clinical and immunologic changes after 1 year of active treatment are the same in the B group as in the A group suggest that the matching and randomization procedures were adequate and that the previously reported successful treatment in the A group was achieved by hyposensitization and was not a chance finding. This conclusion is further supported by the fact that the second year of treatment in the A group resulted in an even more pronounced tolerance to histamine and allergen.