Immunotherapy in cat-induced asthma. Double-blind trial with evaluation of in vivo and in vitro responses

The efficacy of immunotherapy in cat-induced asthma was studied by use of a purified fraction of cat-pelt extract and a double-blind protocol. Nine active-treatment subjects who received a mean cumulative dose of cat allergen, 1 of 10.9 units, and eight placebo-treatment subjects completed the study. Active treatment resulted in significant reductions in bronchial sensitivity ( p < 0.05) and prick test titer ( p < 0.01). In addition, active treatment resulted in a significant delay in the onset of ocular ( p < 0.05) and pulmonary ( p < 0.02) symptoms on exposure to living cats. Significant increases in IgG antibody to cat allergen 1 ( p < 0.001) and cat albumin ( p < 0.01) also occurred with active treatment. There was no significant change in bronchial reactivity to methacholine or in the sensitivity of circulating basophils. These results confirm the validity of immunotherapy in allergic asthma where there is careful patient selection and well defined treatment preparations.