Plasmacytomas with more than one immunoglobulin kappa mRNA: Implications for allelic exclusion

Abstract

Although only one allele of an immunoglobulin gene is thought to be expressed as a polypeptide by a given lymphocyte ('allelic exclusion'), three murine plasmacytomas were found to contain more than one K light chain mRNA species, as evidenced by the sequences of distinct K cDNA clones. Two different K cDNA sequences were cloned from BFPC 61 microsomal mRNA, two from MOPC 173, and three from S107. One cDNA sequence from each tumor matches the known secreted polypeptide, while the variant sequences differ in the variable (V) region. Hence fusion of a V[K] gene to a joining (J[K]) gene has occurred independently on separate homologous chromosomes and each allele is transcriptionally competent...