A study on the immunological basis of the dissociation between type I-hypersensitivity skin reactions to Blomia tropicalis antigens and serum anti-B. tropicalis IgE antibodies

Total IgE levels were similar in the two groups, but α-BtE IgE was significantly higher in the SPT-positive group (SPT+). A large overlap of α-BtE IgE levels was found in individuals of both groups, indicating that these levels alone cannot account for the differences in SPT outcome. Individuals of the two groups did not differ, statistically, in the proportion of α-BtE IgE that reacted with carbohydrate and in the production of IL-10 by BtE- and AlE-stimulated PBMC. Both groups had part of α-BtE IgE activity absorbed out by AlE, indicating the existence of cross-reactive IgE antibodies. However, the α-BtE IgE from the SPT-negative individuals (SPT-) was more absorbed with AlE than the α-BtE IgE from the SPT+ individuals. This finding may be ascribed to avidity differences of the α-BtE IgE that is present in the two groups of individuals, and could occur if at least part of the α-BtE IgE from the SPT- individuals were elicited by A. lumbricoides infection.The present results suggest that a low ratio of specific IgE to total IgE levels (in a minority of individuals), and differences in α-BtE IgE avidities (which would have high affinities for A. lumbricoides antigens in SPT- than in SPT+ individuals) may play a role in the down-modulation of type-I hypersensitivity reaction against aeroallergens described in helminth-infected individuals.Asthma is a complex disease whose phenotypic heterogeneity has been shown to depend both on genetic factors, such as those that underlie the appearance of atopy, and on environmental factors [1,2]. Among the environmental factors, one that is sine qua non in the determination of the development, severity and chronicity of allergic asthma is the contact with environmental allergens, especially those derived from indoor mites, cockroaches, pet epithelia and pollens [3,4]. Indeed, atopy is usually defined as an intrinsic condition characterized by the presence of circulating IgE antibodies against those environmental allergens (i.e., an