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Imprint of somatic hypermutation differs in human immunoglobulin heavy and lambda chain variable gene segments
Laurent Boursier1, Wen Su, Jo Spencer
1Department of Histopathology, Guy's, King's and St Thomas' Medical School, St Thomas' Campus, Lambeth Palace Road, London, SE1 7EH, UK. jo.spencer@kcl.ac.uk
Molecular Immunology
|May 17, 2003
Summary
Somatic hypermutation (SHM) mechanisms differ between immunoglobulin heavy (IgV(H)) and lambda light (IgV(lambda)) chains. Analysis of human intestinal plasma cells reveals distinct mutation patterns and target preferences in IgV(lambda) compared to IgV(H).
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Somatic hypermutation (SHM) diversifies the B cell repertoire by introducing mutations into immunoglobulin (Ig) variable gene segments.
- SHM of Ig heavy chain (IgV(H)) favors transition substitutions and specific 4-mer target sequences (e.g., GRCY).
Purpose of the Study:
- To analyze mutation patterns in human Ig lambda light chain variable gene segments (IgV(lambda)) from intestinal plasma cells.
- To compare SHM mechanisms between IgV(lambda) and IgV(H).
Main Methods:
- Analysis of heavily mutated, nonproductively rearranged IgV(lambda) gene segments.
- Controlling for germline composition and local sequence variability.
Main Results:
- Observed significant G:C strand bias in IgV(lambda).
- Identified differences in di- and trinucleotide target preferences for IgV(lambda) compared to IgV(H).
- Found a tendency for adjacent triplet mutations in IgV(lambda), not typically seen in IgV(H).
Conclusions:
- The mechanism of somatic hypermutation appears to operate differently for human Ig heavy and lambda light chain variable gene segments.
- These findings suggest distinct regulatory or enzymatic processes govern SHM in different Ig loci.