title: Expression of a novel type of immunoglobulin C lambda transcripts in human mature B lymphocytes producing kappa light chains.
abstract: Ordered rearrangement of immunoglobulin genes (heavy chain then kappa and eventually lambda genes) is observed during B lymphocyte ontogeny. Unexpectedly, we found that human mature B cells producing kappa chains and having germ-line lambda genes contain lambda mRNA consisting of an invariant 5' region (herein termed X) and of one of the classical C lambda exons. The X region of these transcripts originates from a unique exon located 5 kb upstream of the J-C lambda 1 gene segment. X-C lambda mRNA expression occurs without somatic DNA rearrangement. The use of the X DNA fragment as a probe allows definition of a family of human genes that comprises at least four members and includes the first exon of the lambda 14.1 gene. The latter is selectively transcribed in pre-B lymphocytes and directs the synthesis of a lambda-like chain. In contrast, the X-C lambda transcripts do not appear to encode a C lambda-related polypeptide in mature B cells. Thus, despite a 73% homology extending far beyond the exon sequences, the X and lambda 14.1 genes are expressed at different stages of B cell development and might serve different functions.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Hôpital Saint Louis, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Guglielmi
authors.forename: F
authors.initials: F
authors.lastname: Davi
mesh_terms: D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D002460:Cell Line; D002999:Clone Cells; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation / Q000276:immunology; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007147:Immunoglobulin Light Chains / Q000096:biosynthesis*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D007127:Immunoglobulin Constant Regions; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains