LONG-TERM FOLLOW-UP OF PATIENTS TREATED WITH A 3-YEAR COURSE OF CAT OR DOG IMMUNOTHERAPY

Background: A 5-year follow-up study was conducted to investigate the duration of the effects of a 3-year course of immunotherapy with stand ardized cat or dog extracts in 32 children and adults with asthma caus ed by animal dander. Methods: Thirty of the subjects could be reached with a questionnaire, 19 underwent bronchial allergen and histamine ch allenges and four had only a histamine challenge. Specific IgE and IgG (4) levels in serum were measured in those who underwent challenges. R esults: Almost all subjects (26 of 30) reported no change (17 subjects ) or increased tolerance (9 subjects) on exposure to cats or dogs. In contrast, 17 of the 19 who underwent allergen challenges had increased allergen sensitivity compared with when therapy was stopped (p < 0.01 ), and the results were no longer significantly different from before therapy was started. Mean provocative concentration of histamine causi ng a 20% fall in peak expiratory flow was, however, still higher than before therapy in the cat immunotherapy group (p < 0.01) and had not c hanged significantly during the follow-lip period. In the dog immunoth erapy group there was no significant change during or after therapy. S pecific IgG(4) had decreased, and specific IgE in serum had remained l ow and was comparable to the levels measured at the end of the study p eriod. Conclusions: Five yeats after stopping immunotherapy, objective ly measured bronchial allergen sensitivity had increased and had appro ached pretreatment conditions. Asthma symptoms, according to patients' subjective evaluations had continued to be mild in most patients, and bronchial histamine sensitivity had remained stable. These observatio ns could reflect remaining effects of immunotherapy or the natural his tory of mild asthma.