Biased Iglambda expression in hypermutated IgD multiple myelomas does not result from receptor revision.
Normal IgM(-)IgD(+) CD38(+) B cells and IgM(-)IgD(+) multiple myelomas (MM) are characterized by Cmu deletion, biased Iglambda expression and hypermutated IgV regions. The predominant Iglambda usage has been proposed as resulting from secondary Ig gene rearrangements during extensive clonal expansion in the germinal center environment. Here, four cases of IgDlambda MM were studied to address the question of light chain receptor revision in a 'single cell' model. Detailed analyses of both IGK and IGL alleles of each case were performed by Southern blotting, (RT-) PCR, and sequencing. The expressed IgV genes were extensively mutated and Cmu deletion was confirmed in two cases. In addition, in the four MM a total of six non-functional deletional IGK rearrangements were identified, which proved to be unmutated. We conclude that IgD myelomas indeed originate from (post) germinal center B cells in which, in spite of the fact that they are hypermutated, there is no evidence of receptor revision.
van der Burg
M
M
Dept of Immunology, Erasmus University Rotterdam/University Hospital Rotterdam, The Netherlands.
Bende
R J
RJ
Aarts
W M
WM
Langerak
A W
AW
van Dongen
J J M
JJ
van Noesel
C J M
CJ
D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology; D001483:Base Sequence; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain; D006801:Humans; D007072:Immunoglobulin D / Q000235:genetics*; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007146:Immunoglobulin lambda-Chains / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009101:Multiple Myeloma / Q000235:genetics* / Q000276:immunology; D009154:Mutation; D011947:Receptors, Antigen, B-Cell / Q000235:genetics
D007072:Immunoglobulin D; D007147:Immunoglobulin Light Chains; D007146:Immunoglobulin lambda-Chains; D011947:Receptors, Antigen, B-Cell