SPECIFICITY ENHANCEMENT OF POLYCLONAL ANTISERA BY THE INDUCTION OF TOLERANCE TO UNWANTED CROSS-REACTING DETERMINANTS

Steroids form a structurally closely related group. As a result, antib odies produced for use in immunoassays regularly show unwanted cross-r eactivities, These may be reduced by altering hapten-protein coupling procedures, thereby reducing the exposure of the determinants giving r ise to the undesirable cross-reaction. However, these procedures carl prove to be complex, expensive and nor totally predictable in outcome. Exploitation of the clonal selection theory is an attractive alternat ive approach. The host is primed with the interfering cross-reactant c oupled to a non-immunogenic amino acid copolymer to inactivate the B-l ymphocyte clones specific for this steroid, producing a specific immun otolerance. Then, 3 days Inter, the host is immunized with the steroid against which nn antibody is required. The clones producing antibody to this immunogen are unaffected and the cross-reactivity is significa ntly reduced or deleted The technique has been applied to the reductio n of endogenous sex steroid cross-reactivity from antibodies prepared against synthetic and semi-synthetic androgens (17 alpha-methyltestost erone, 19-nor-beta-testosterone) and the progestogen medroxyprogestero ne. Antibodies prepared against the synthetic oestrogen zeranol using this technique have significantly reduced its undesirable cross-reacti vity with the fungal metabolite 7 alpha-zearalenol. Highly specific an tisera have been generated in all cases, the only adverse effect being a reduction in the titres achieved in comparison with rabbits receivi ng the conventional immunizing regime.