Antisera were raised in rabbits against immunosorbent-purified F(ab′)2 fragments of IgG antitetanus toxoid (TT) antibodies obtained from three different donors. The antisera were rendered idiotype specific by absorption with insolubilized TT-nontreactive F(ab′)2. The resulting anti-idiotypic antisera precipitated more than 85% of 125I-radiolabeled F(ab′)2 anti-TT and were shown to be individual specific in that they reacted only with the immunizing F(ab′)2 anti-TT and not with F(ab′)2 anti-TT derived from other donors. Anti-idiotypic antiserum inhibited binding of 125I-TT but not of 125I-DT to IgG derived from the donor of the immunizing F(ab′)2 anti-TT, but did not inhibit 125I-TT binding to IgG derived from other donors. Binding of radiolabeled TT to IgM and IgE was significantly inhibited by the anti-idiotypic antiserum, demonstrating the presence of shared idiotypic determinants on anti-TT antibody molecules belonging to the IgG, IgM, and IgE classes of immunoglobulin. Finally, binding of 125I-F(ab′)2 anti-TT to the antiidiotypic antiserum was completely inhibited by IgG derived from the same donor but only partially inhibited by a great excess of TT antigen, suggesting that the antiidiotypic antiserum is recognizing nonantigen-binding idiotypic determinants on F(ab′)2 anti-TT. The data presented demonstrate that anti-idiotypic heteroantisera can be successfully raised against human antibodies to TT, indicate minimal cross-reactivity of idiotypic determinants between unrelated individuals, and suggest the presence of nonantigen binding-idiotypic determinants on the antibody molecule.

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This work was supported by a grant from the Charles H. Hood Foundation and by United States Public Health Service Grants AI 05877 and AI 11419.

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