Three epitope-specific monoclonal antibodies against the hapten penicillin.

Three monoclonal antibodies (Pen 4, Pen 7 and Pen 9) were raised against the benzylpenicilloyl group and used to investigate the antigenicity of this group. The binding of Pen 4 to carrier-bound penicillin derivatives was shown in an ELISA to be dependent on the structure of the side chain in the derivative. Hence Pen 4 recognizes this side chain. From the difference in binding to carrier-bound penicillin derivatives in a competitive enzyme immunoassay it was concluded that Pen 7 mainly recognizes the new antigenic determinant which emerges from the binding of the penicillin derivative to a carrier. The binding of Pen 9 to carrier-bound penicillin derivatives was not influenced by the nature of the side chain. Neither was the bound or free nature of the derivative of influence on the binding. Therefore it is concluded that Pen 9 mainly recognizes the thiazolidine ring of penicillin. This study thus shows that in the benzylpenicilloyl group at least three epitopes can be recognized.