title: Memory B lymphocytes in human tonsil do not express surface IgD.
abstract: To clarify the phenotype of memory B lymphocytes, we have determined the frequency of somatic hypermutations in purified tonsil B cell populations. Our particular interest was the controversial question of whether any memory B-cells express IgD. Ig heavy chain gene rearrangements that used the nonpolymorphic VH6 gene were amplified by PCR, cloned, and sequenced. All eight sequences obtained from the surface IgD (sIgD)-negative fraction contained point mutations, with frequency of one mutation in every 24 bases of sequence. In contrast, only 4 of 12 sequences obtained from the sIgD-positive fraction contained point mutations, with a mutation frequency of one in 600. This frequency was similar to that found for cord blood B cells (one in 550), a population that does not contain memory B cells. These results indicate that although memory B cells are present in the sIgD-negative fraction, no memory cells can be detected in the sIgD-positive fraction of tonsil B lymphocytes.
authors: Department of Clinical Immunology, Flinders Medical Centre, Bedford Park, Australia.
authors: I C
authors: IC
authors: Nicholson
authors: M J
authors: MJ
authors: Brisco
authors: H
authors: H
authors: Zola
mesh_terms: D000595:Amino Acid Sequence; D016175:B-Lymphocyte Subsets / Q000276:immunology; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry; D015322:Gene Rearrangement, B-Lymphocyte / Q000235:genetics*; D006801:Humans; D007072:Immunoglobulin D / Q000235:genetics* / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007156:Immunologic Memory / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D014066:Palatine Tonsil / Q000166:cytology; D016133:Polymerase Chain Reaction
chemical_list: D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D004247:DNA