A second rabbit kappa isotype.

Abstract

IgG from the rabbit strain Basilea was previously shown to contain 2 distinct populations of molecules, one with light [L] chain belonging to the known .lambda. isotype and the others to a new .kappa.-like L chain type. Alloantisera prepared against the Basilea IgG are directed against the .kappa.-like light chain (anti-bas antisera). All Basilea rabbits express .kappa.-like chains recognized by anti-bas sera, but IgG from other domestic rabbits did not react with these antisera. Genetic studies of wild rabbits belonging to different populations show that the bas+ phenotype could be found in heterozygous rabbits and those homozygous at the b locus. The gene encoding the bas+ light chain is closely linked to the B locus. Antigenic determinants recognized by anti-bas antibodies and antigenic determinants recognized by antibodies directed against allotypic determinants of the b series are located on distinct IgG molecules. There are 2 rabbit .kappa. isotypes: the .kappa.1 isotype, bearing allotypic determinants of the b series, and the .kappa.2 isotype, for which bas+ chain is one of the allotypic forms. The .kappa.1 and .kappa.2 isotypes are controlled by closely linked genes.