Analyses of the splenic mRNA expressed by rabbits of different immunoglobulin kappa-light chain allotypes: conserved sequences in the 3' untranslated region and allotype-specific probes.

The allelism of the structural genes for the complex rabbit b allotypes of immunoglobulin kappa-light chains has been questioned because of observations of unexpected phenotypic expression of "latent" allotypes. We find that the coding sequences of the b4 and b5 "alleles" are only 80% homologous for the last 60 nucleotides but there is a high degree of homology (96%) in the 3' untranslated region (3'DT). The high conservation of 3' DT region sequences enabled us to detect kappa-light chain mRNAs from rabbits of different genetic types (b4, b5, b9 and bbas) on northern blots and dot blots. We can distinguish mRNA encoding b9 and b5 allotypes on dot blots with b5 fragment-probes of known sequence and detect mRNA produced by unstimulated cultured splenic lymphocytes. Analyses of mRNA from cultured cells manipulated to enhance mRNA synthesis and production of unexpected or "latent" b allotypes can now be conducted.