Comparative studies on tree-pollen allergens. V. Immunochemical mapping of the antigens and allergens of birch pollen extract (Betula verrucosa).

A comparative electrophoretic and autoradiographic analysis of the different fractions of birch pollen crude extract was performed. This extract included a minimum of 17 reproducible and distinct antigens located in the gel filtration fractions BV2-BV4. Only one of these precipitates had the ability to bind IgE, as demonstrated by immunoelectrophoretic and autoradiographic techniques using several poly- and monospecific rabbit antibodies. The allergenicity of the different fractions was examined in vitro by RAST and RAST inhibition, and in vivo by passive cutaneous transfer and skin prick tests. The data suggested that Betula verrucosa pollen extract contains a group of isoallergens with related antigenicity but with variable molecular sizes. The findings have also confirmed the presence of identical antigenic properties of the previously isolated pI 5.18 and BV45 as deduced from their immunoelectrophoretic and autoradiographic studies.