title: Evidence for preferential Ig gene usage and differential TdT and exonuclease activities in human naïve and memory B cells.
abstract: Memory B cells and the antibodies they encode are important for protective immunity against infectious pathogens. Characterization of naïve and memory B cell antibody repertoires will elucidate the molecular basis for the generation of antibody diversity in human B cells and the optimization of antibody structures that bind microbial antigens. In this study we aimed to investigate the influence of antigenic selection on the antibody genes of the two CD27+ memory B cell subsets, comparing them with the naïve repertoire in CD27- cells. We analyzed and compared the Ig heavy chain gene transcripts in three recently defined circulating naïve and memory B cell subsets (CD19+IgD+CD27- [naïve], CD19+IgD+CD27+ [un-class-switched memory] or CD19+IgD- CD27+ [class-switched memory]) at the single cell level. We found similar biased patterns of variable, diversity and joining heavy chain gene usages in all three groups of cells. CD19+IgD+CD27+ memory B cells harbored as diverse an antibody gene repertoire as CD19+IgD-CD27+ memory B cells. Interestingly, CD19+IgD+CD27+ memory B cells possessed a lower frequency of somatic mutations, a higher incidence of exonuclease activity at the 3' end of D regions, and a lower frequency of N and P nucleotide additions at both VH-D and D-JH junctions of CDR3 regions compared to CD19+IgD-CD27+ memory B cells. These data suggest distinct functional mechanisms underlying selection of this unique subset of un-class-switched memory B cells.
authors.affiliation: Department of Pediatrics, Vanderbilt University Medical Center, 21st Avenue South, Nashville, TN 37232, USA.
authors.forename: Cuixia
authors.initials: C
authors.lastname: Tian
authors.forename: Grace K
authors.initials: GK
authors.lastname: Luskin
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Dischert
authors.forename: James N
authors.initials: JN
authors.lastname: Higginbotham
authors.forename: Bryan E
authors.initials: BE
authors.lastname: Shepherd
authors.forename: James E
authors.initials: JE
authors.lastname: Crowe
mesh_terms: D000328:Adult; D020816:Amino Acid Motifs; D000818:Animals; D018941:Antigens, CD19 / Q000276:immunology; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D001782:Blood Donors; D002469:Cell Separation; D002999:Clone Cells; D022801:Complementarity Determining Regions / Q000737:chemistry / Q000276:immunology; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism*; D005092:Exonucleases / Q000378:metabolism*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D005803:Genes, Immunoglobulin / Q000235:genetics*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology; D007132:Immunoglobulin Isotypes / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology; D007156:Immunologic Memory / Q000276:immunology*; D051379:Mice; D009154:Mutation / Q000235:genetics; D009711:Nucleotides; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology
chemical_list: D018941:Antigens, CD19; D022801:Complementarity Determining Regions; D007143:Immunoglobulin Heavy Chains; D007132:Immunoglobulin Isotypes; D007135:Immunoglobulin Variable Region; D009711:Nucleotides; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7; D004253:DNA Nucleotidylexotransferase; D005092:Exonucleases