SYNGENEIC ANTIIDIOTYPIC MONOCLONAL-ANTIBODIES AGAINST AN ANTI-HUMAN CHORIONIC-GONADOTROPIN ANTIBODY

Monoclonal antibody designated 1B10 (Mab 1B10) has been shown to be hi ghly specific for the beta-chain of human chorionic gonadotrophin (HCG ). We used this antibody to investigate its paratope using anti-idioty pic antibodies. Purified Mab 1B10 has been used to immunize syngeneic BALB/c mice to produce anti-idiotypic monoclonal antibodies. An enzyme immunoassay (ELISA) on Mab 1B10 coated plate was employed to screen t he supernatants of growing hybridomas. The specificity of each antibod y selected was assessed using an inhibition ELISA and immunoblotting. Monoclonal antibodies belonging to two categories were selected. (a) T hose (designated Mab 4F8 and Mab 7G9) recognizing epitopes of the Ig m olecule located in/or near the antigen-binding site of Mab 1B10. In EL ISA these antibodies were shown to inhibit in a dose-dependent manner, the reaction of Mab 1B10 with its specific antigen; (b) those (Mab 2B 8, Mab 3B8) reacting with epitopes located outside of the antigen bind ing site of the antiHCG antibody molecule and did not influence the re actions of Mab 1B10 and its antigen. Following immunization of syngene ic BALB/c mice monoclonal antibodies (Mab 4F8, Mab 7G9) were produced which recognized epitopes located on the variable region of Mab 1B10 s ince they did not react with other murine monoclonal antibodies of the same isotype. These antibodies inhibited the binding of Mab 1B10 to i ts corresponding epitope on the molecule of HCG and they can be define d as syngeneic anti-idiotypic antibodies.