V(H) gene replacement occurs in the spleen and bone marrow of non-autoimmune quasi-monoclonal mice.
Genes encoding the heavy chain portion of immunoglobulin molecules arise from the combinatorial association of V, D and J gene segments, which occurs during discrete stages of B lineage development in the bone marrow. Recently, V(H) replacement, a form of receptor editing, has been described, in which the variable region of an existing VDJ(H) rearrangement is replaced by another V(H) gene segment in a recombination event believed to involve an embedded heptamer within the coding region of the V(H). Studies of transgenic mice with "knocked-in" VDJ(H) genes encoding anti-DNA specificity have demonstrated that receptor editing of the heavy chain is one mechanism by which autoreactive B cell receptors can be modified. Another mouse, the "quasi-monoclonal", which encodes a "knocked-in" VDJ(H) for the hapten NP also contains B lineage cells that undergo V(H) replacement. This suggests that V(H) replacement may play a role in the normal diversification of the antibody repertoire. Using a ligation-mediated PCR assay, we have identified V(QM) double-stranded DNA breaks indicative of V(H) replacement intermediates from bone marrow and splenic B lineage cells of quasi-monoclonal mice in the absence of immunization. V(QM) to J558 recombination deletion products consistent with V(H) replacement were also detected in both the bone marrow and spleen of non-immunized quasi-monoclonal mice. Moreover, RAG-1 transcripts were detected in the spleen. These data suggest that V(H) replacement can be part of the mechanism(s) used by B lineage cells to generate diversity throughout B lineage development, including later stages occurring in secondary lymphoid tissues.
Bertrand
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FE
The Ontario Cancer Institute and Department of Immunology, University of Toronto, Canada. bertr010@tc.umn.edu
Golub
R
R
Wu
G E
GE
D000818:Animals; D000943:Antigens, Differentiation / Q000096:biosynthesis; D001483:Base Sequence; D001853:Bone Marrow / Q000276:immunology*; D004249:DNA Damage; D018076:DNA, Complementary; D015870:Gene Expression; D015322:Gene Rearrangement, B-Lymphocyte; D005803:Genes, Immunoglobulin; D018398:Homeodomain Proteins / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D013154:Spleen / Q000276:immunology*
D000943:Antigens, Differentiation; D018076:DNA, Complementary; D018398:Homeodomain Proteins; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region; C096712:antigen GL7; C064658:RAG-1 protein