The origin of low-grade mucosa-associated lymphoid tissue (MALT)-type B- cell lymphoma is still unclear. Using a novel two-step procedure, we have sequenced the Ig VH genes expressed by cells from four patients with gastric low-grade MALT-type lymphoma. The nucleotide sequences of the complementarity determining region 3 (CDR3) of the genomic DNA were first amplified using consensus oligonucleotide primers, then sequenced. Based on the CDR3 sequence amplified from each MALT lymphoma, individual tumor-specific primers were synthesized and used directly in the polymerase chain reaction (PCR) to analyze the sequences of their Ig heavy-chain variable region. When compared with the germ-line sequence, many nucleotide substitutions, mainly in the CDRs, were found in the variable gene sequences of the four MALT lymphomas. The mutations showed a high replacement-to-silent ratio and were distributed in a way which suggested that the tumor cells had been positively selected through their antigen receptor. Our findings indicate that the MALT-type lymphoma B cells are hypermutated postgerminal center lymphocytes that have undergone antigen selection.
Somatic hypermutation in low-grade mucosa-associated lymphoid tissue- type B-cell lymphoma
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Y Qin, A Greiner, MJ Trunk, B Schmausser, MM Ott, HK Muller-Hermelink; Somatic hypermutation in low-grade mucosa-associated lymphoid tissue- type B-cell lymphoma. Blood 1995; 86 (9): 3528–3534. doi: https://doi.org/10.1182/blood.V86.9.3528.bloodjournal8693528
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