Specific isolation and characterization of antibody directed to binding site antigenic determinants

The preparation and specificity of antibodies specific for the ligand-binding site of HOPC 8, a phosphorylcholine (PC)-binding mouse myeloma protein, are described. Antiserum to HOPC 8, prepared in rabbits, was adsorbed with an HOPC 8-Sepharose immunoadsorbent and anti-binding site antibodies were eluted with PC. These antibodies reacted with HOPC 8 but not other myeloma proteins, including those with PC-binding specificity different from HOPC 8; the specificity of this anti-HOPC 8 antibody for the combining site region of HOPC 8 was shown by the fact that 1) the interaction of the anti-HOPC 8 antibody preparation with HOPC 8 was completely blocked by PC and 2) the antibody preparation failed to bind TEPC 15 in which the combining sites had been blocked by covalently bound PC groups. Moreover, these anti-binding site antibodies did not react with isolated heavy or light chains, indicating the requirement for a heavy-light chain interaction. By contrast an idiotypic antiserum to HOPC 8 prepared in A/J mice did bind affinity-labeled TEPC 15 and the reaction with HOPC 8 was only marginally hapten inhibitable. Both of the idiotypic determinants detected by these two antisera were present on anti-PC antibody raised in BALB/c mice;