Delineating the specificity of an IgE-encoding transcriptome.

BACKGROUND Although much is known about the reactivity of polyclonal populations of antibodies targeting the wide array of allergens produced by timothy (Phleum pratense) and other grass species, little is known about the finer details at the level of individual antibody specificities. OBJECTIVE We sought to investigate the IgE repertoire as it occurs in a patient with grass pollen allergy. METHODS For this purpose, a human IgE library was used, constructed from peripheral blood B cells of an individual with timothy allergy. The library was screened by using phage display against a panel of 6 timothy allergens (Phl p 1, Phl p 2, Phl p 4, Phl p 5, Phl p 6, and Phl p 11). RESULTS Highly diverse antibody fragments with respect to gene usage were identified. The binders were specific for their respective target antigen, except for clones selected on Phl p 6 that also recognized Phl p 5, most likely reflecting the high sequence homology between these allergens. Interestingly, by using this approach, we were able to determine the specificity of more than 25% of all IgE-producing transcripts in this individual with allergy. CONCLUSION The human IgE repertoire is produced by a limited number of highly related B-cell clones and as such is restricted in its recognition of a limited number of antigens. CLINICAL IMPLICATIONS Human allergen-specific antibodies can, by defining the specificity of IgE responses, aid in the development of allergy vaccines or even by themselves be used in passive immunotherapy.