NONSPECIFIC CHANGES IN IMMUNOTHERAPY WITH HOUSE-DUST EXTRACT

Despite the possible complications and inadequacies of the immunothera py of allergic patients with house dust extracts (HDE), this is widely applied in Latin America and is commonly considered to be a cost-effe ctive treatment for allergic diseases. Doubts about its efficacy and m echanism of action prompted us to evaluate the immunological changes t hat occurred in a group of 99 patients selected for their confirmed al lergic sensitivity to house dust, and who showed significant clinical improvement after a minimum of 12 months of immunotherapy with HDE. Th e favorable clinical response of these patients was associated with so me of the mechanisms reported for immunotherapy with pollen or venom a llergens, such as increased levels of IgG or IgG4 ''blocking'' antibod ies, and the increased affinity of these antibodies for house dust ant igens, or diminished basophil sensitivity to HDE. However, the magnitu de of these changes was relatively small, and their biological signifi cance questionable. In contrast, particularly evident was a reduction in the cutaneous reactivity not only to the specific allergen, but als o to the nonspecific mast cell degranulator codeine and to histamine. These results suggest that as yet unidentified ''nonspecific'' mechani sms might contribute to the effect of immunotherapy with extracts as h eterogeneous and complex as HDE.