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Class switch from μ to δ is mediated by homologous recombination between σ μ and σ μ sequences in human immunoglobulin gene loci
Author(s) -
Yasui Hisashi,
Akahori Yasushi,
Hirano Masami,
Yamada Kazumasa,
Kurosawa Yoshikazu
Publication year - 1989
Publication title -
european journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 201
eISSN - 1521-4141
pISSN - 0014-2980
DOI - 10.1002/eji.1830190808
Subject(s) - immunoglobulin d , biology , microbiology and biotechnology , genetics , intron , homologous recombination , immunoglobulin class switching , gene , dna , recombination , sister chromatids , antibody , chromosome , b cell
Abstract Class switch of immunoglobulin from μ to γ occurs by recombination between two repetitive switch sequences: S μ and S γ . However, there are no such sequences in the μ‐δ introns of human and mouse genomes. Although the frequency of IgD‐secreting cells is extremely low in mouse about 1% of patients with myeloma produce IgD in human. In a previous report ( Nucleic Acids Res. 1988. 16 : 9497) we reported that a 442‐bp DNA sequence located in the J H‐μ intron (defined as σ μ ) was inserted into the μ‐δ intron (defined as σ μ ) in the human genome. There is no such insertion in mouse. We analyzed Ig H chain gene loci of two human IgD myelomas: one was analyzed by cloning and sequencing and the other by Southern hybridization. We found that recombination had occurred between these two homologous DNA sequences, resulting in loss of the DNA segment from σ μ to σ μ On the other hand, in a Burkitt lymphoma, Daudi, the DNA fragment from σ μ to σ μ was duplicated. These results suggest that homologous recombination between σ μ and σ μ sequences mediates class switch from μ to δ in human and that it occurs via unequal crossing‐over between sister chromatids or daughter chromosomes.