The immune response to bacterial dextrans. IV. Antibody idiotypes.

Anti-idiotypic antisera (a-Id) were prepared in SJL mice against the dextran B512 (Dex)-specific hybridoma antibody D.16.6 (mu, kappa) of C57BL/6 origin. Such a-Id were specific for the D.16.6 antibody, but the idiotypic determinants recognized were not hapten modifiable. The a-Id were used in radioimmunoassays (RIA) to study the genetic control of the expression of the D.16.6 idiotype (Id) in a variety of mouse strains. It was found that all mouse strains tested expressed this Id as a component of the normal background immunoglobulin (Ig) in their sera. Only in mice of the IgCHb haplotype, however, was the Id found in association with Dex-specific antibodies. Furthermore, even in IgCHb mouse strains, not all individuals expressed Id-positive anti-Dex antibodies. Because the D.16.6 Id is a "recurrent" natural Id, but a "non-dominant" Id in the Dex response of IgCHb mouse strains, these observations contradict our previous suggestions on the selection of "dominant" Id from the pool of "naturally" produced Ig.