Molecular analysis of IgD-positive human germinal centres.
It is controversially discussed whether human IgM(+)IgD(+)CD27(+) B cells, which carry somatically mutated Ig variable region (IgV) genes, are derived from germinal centres (GC) B cells or originate from another developmental pathway. GC composed of IgM(+)IgD(+) B cells, which co-express the CD70 surface marker, have been described in approximately 10% of tonsils. As IgM(+)IgD(+)CD27(+) B cells might be generated in such GC, we characterized IgD(+) tonsillar GC cells. GC dominated by IgD(+) B cells were present in 10 of 67 tonsils analyzed. Three GC were additionally positive for CD70. Detailed analysis of one such GC by microdissection and single-cell DNA PCR revealed IgD(+) GC B cells undergoing somatic hypermutation during clonal expansion. However, further analysis of this GC as well as five additional microdissected GC by reverse transcription (RT)-PCR for clonally related Igmu and Igdelta transcripts indicated that the B-cell clones in five of these six IgD(+) GC belong to the IgD-only B cell subset, which has deleted the Cmu gene, and that only one GC harboured a large IgM(+)IgD(+) B-cell clone. Hence, most IgD(+) GC consist of IgD-only B cells and fully developed IgM(+)IgD(+)(CD70(+)) GC are very rare. This indicates that the rare IgM(+)IgD(+) GC B-cell clones from IgD(+) GC contribute little to the large population of IgM(+)IgD(+)CD27(+) B cells. Finally, an RT-PCR analysis with clone-specific primers for two IgD(+) GC B-cell clones showed an absence of IgG or IgA class-switched clone members, indicating strict regulation of class switching and a selective production of IgD(+) B cells from such clones.
Institute of Cell Biology (Cancer Research), Medical School, University of Duisburg-Essen, Virchowstrasse 173, 45122 Essen, Germany.
Claudia
C
Müller
Dörte
D
Siemer
Götz
G
Lehnerdt
Stephan
S
Lang
Ralf
R
Küppers
D000293:Adolescent; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D053282:CD27 Ligand / Q000096:biosynthesis; D002452:Cell Count; D002648:Child; D004247:DNA / Q000235:genetics; D018858:Germinal Center / Q000276:immunology*; D006801:Humans; D007072:Immunoglobulin D / Q000096:biosynthesis*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007150:Immunohistochemistry; D009154:Mutation; D014066:Palatine Tonsil / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D027041:Somatic Hypermutation, Immunoglobulin
D053282:CD27 Ligand; D007072:Immunoglobulin D; D007135:Immunoglobulin Variable Region; D004247:DNA