Limited junctional diversity in kappa light chains. Junctional sequences from CD43+B220+ early B cell progenitors resemble those from peripheral B cells.
Among all adult T and B cell Ag receptor chains, only Ig light chains lack N regions. It is thought that this is due to the fact that light chain genes rearrange after heavy chain genes, and that terminal deoxynucleotidyl transferase, the enzyme that adds N regions, is not longer expressed at that stage. However, this concept has been challenged recently by the demonstration that 3 to 10% of B cell precursors (CD43+B220+) appear to rearrange their light chains at approximately the same time as they undergo VH-->DJ rearrangements. To examine N region addition in B cell precursors undergoing early kappa-chain rearrangement, we PCR amplified rearranged V kappa 21 genes from the CD43+B220+ bone marrow cells and compared them to sequences obtained from whole bone marrow and spleen. Unexpectedly, all three populations showed approximately 10% N region containing junctions, most consisting of only one N nucleotide. Thus, even the B cell precursors that rearrange light chains at this early stage of development lack much N region diversity. Twelve percent of the sequences unambiguously contained P regions, which were from 1 to 5 nucleotides in length. All but 2 of the 41 productive rearrangements had the commonly observed CDR3 length of nine amino acids. Many (71%) of the sequences were out of frame. CDR3 length was very restricted in nonproductive rearrangements too, and deletion of nucleotides from V kappa and J kappa gene segments was limited. Thus, even at the level of nonproductive rearrangements, junctional diversity is minimal for kappa-chains.
Victor
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KD
Scripps Research Institute, Department of Immunology, La Jolla, CA 92037.
Vu
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Feeney
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D000818:Animals; D000916:Antibody Diversity; D015703:Antigens, CD; D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D001483:Base Sequence; D001854:Bone Marrow Cells; D002454:Cell Differentiation; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D005803:Genes, Immunoglobulin; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D017493:Leukocyte Common Antigens; D051917:Leukosialin; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012795:Sialoglycoproteins / Q000032:analysis; D013154:Spleen / Q000166:cytology
D015703:Antigens, CD; D000954:Antigens, Surface; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; D051917:Leukosialin; D012795:Sialoglycoproteins; C497863:Spn protein, mouse; D017493:Leukocyte Common Antigens