Analyses of the splenic mRNA expressed by rabbits of different immunoglobulin κ-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 κ-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'UT). The high conservation of 3' UT region sequences enabled us to detect κ-light chain mRNAs from rabbits of different genetic types (b⁴, b⁵, b⁹ and b(bas)) 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.