Clinical manifestations of type 1 hyperreactivity are triggered when allergens cross-link effector cell-bound IgE and aggregate the underlying high affinity FcϵRI. While the IgE antibody-mediated release of mediators constitutes the immunopathological basis for immediate symptoms, much less is known concerning the role of allergen-specific responses of isotypes other than IgE.

Our analysis of the major birch pollen (Betv1) specific immune response showed for the first time that Betv1 specific memory B cells are present in tonsils and peripheral blood of both atopic and non-atopic individuals.

RT-PCR of single Betv1 specific B cells revealed highly mutated sequences mainly of the IgG and IgA isotype. Striking was the high percentage of VH3-30 or VL3l gene rearrangements. This result was confirmed by an in vitro antibody affinity selection via phage panning of a human VH/VL phage library (Griffin.1) using recombinant Betv1. Recombinant antibodies with VH3-30 or VL3l rearrangement had the highest relative affinities as measured by plasmon resonance technology.

As Betv1 plasma cells were detectable in tonsils only in atopic individuals, the question rises, how the differentiation of Betv1 specific memory B cells in non-atopic individuals is controlled and why Betv1 specific IgE antibodies as in case of atopic disease are not synthesized.