IGG AND IGE ANTIBODIES IN SUBJECTS ALLERGIC TO PENICILLINS RECOGNIZE DIFFERENT PARTS OF THE PENICILLIN MOLECULE

Background: IgE and IgG antibodies to penicillins can have different s pecificities. However, this response, including the recognition of the different parts of penicillin, has never been studied in the same sub ject. Objective: Study of the specificity of IgE and IgG antibodies an d the relevant parts of the penicillin molecule that contribute to the hapten binding: site in sera from human. Methods: Specific IgE antibo dies were determined by RAST and specific IgG antibodies by ELISA. The recognition of the different molecules was studied by inhibition stud ies. Results: Seven sera with IgG and IgE antibodies to amoxicillin an d benzyl penicillin were analyzed. IgE antibodies recognized mainly tw o different epitopes: in one, the side chain was a relevant part of th e epitope, in the other, it was the nuclear portion. IgG antibodies re cognized the nuclear portion in all instances. In the same subject, an tibodies of different isotype and specificity were found. Conclusions: Subjects who develop simultaneously IgE and IgG antibodies to penicil lins show different specificities. This proves that different populati ons of antibodies recognize different epitopes.