B-cell epitopes recognized by IgE from patients sensitive to Amb a 5


A. Rosenberg, Section of Allergy, Department of Medicine, University of Minnesota, Minneapolis 55455. USA.


Background The response to allergens characterized hy IgE-mediated hypersensitivity is selective. The search for the inherited contribution to atopy has among other things, focused on the linkage of sensitivity to the presence of specific alleles in the DR and DQ locus. More than 90% of the responders to Amb a 5, an allergen from ambrosia artemisifolia, are DR-2 positive. This relationship is logically linked to the T-cell epitope presentation by the HLA complex.

Objectives This study aims to investigate a possible relationship between T-cell epitopes. B-cell epitopes and the alleles of the DR and DQ loci in Amb a 5 sensitive DR-2+ and DR-2 – individuals.

Methods Inhibition of solid state Elisa assays by IgE-enriched and IgG-depleted, heated sera. The inhibition was carried out in checkerboard pattern, bidirectionally; A inhibits B and B inhibits A.

Results The B-cell epitopes defined hy the inhibition pattern were all found to be conformational. Three different epitope patterns (A, B, C) were recognized. The IgE and IgG complexes were found in only one responder. The DR and DQ locus alleles were all sequenced. Although all the individuals studied responding to Amb a 5 show presence of alleles such as 1501, associated with DR-2, our data indicates no correlation between the B-cell epitopes recognized and the DR and DQ locus alleles. A well known, general T-cell motif was recognized in the known sequence of Amb a 5.

Conclusions Our investigation suggests that the choice of B-cell recognition is regulated independently of a putative link between T-cell epitope recognition and the D locus.