title: Secondary immunization generates clonally related antigen-specific plasma cells and memory B cells.
abstract: Rechallenge with T cell-dependent Ags induces memory B cells to re-enter germinal centers (GCs) and undergo further expansion and differentiation into plasma cells (PCs) and secondary memory B cells. It is currently not known whether the expanded population of memory B cells and PCs generated in secondary GCs are clonally related, nor has the extent of proliferation and somatic hypermutation of their precursors been delineated. In this study, after secondary tetanus toxoid (TT) immunization, TT-specific PCs increased 17- to 80-fold on days 6-7, whereas TT-specific memory B cells peaked (delayed) on day 14 with a 2- to 22-fold increase. Molecular analyses of V(H)DJ(H) rearrangements of individual cells revealed no major differences of gene usage and CDR3 length between TT-specific PCs and memory B cells, and both contained extensive evidence of somatic hypermutation with a pattern consistent with GC reactions. This analysis identified clonally related TT-specific memory B cells and PCs. Within clusters of clonally related cells, sequences shared a number of mutations but also could contain additional base pair changes. The data indicate that although following secondary immunization PCs can derive from memory B cells without further somatic hypermutation, in some circumstances, likely within GC reactions, asymmetric mutation can occur. These results suggest that after the fate decision to differentiate into secondary memory B cells or PCs, some committed precursors continue to proliferate and mutate their V(H) genes.
authors.affiliation: Department of Medicine, Rheumatology, and Clinical Immunology, Charité University Medicine Berlin, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Frölich
authors.forename: Claudia
authors.initials: C
authors.lastname: Giesecke
authors.forename: Henrik E
authors.initials: HE
authors.lastname: Mei
authors.forename: Karin
authors.initials: K
authors.lastname: Reiter
authors.forename: Capucine
authors.initials: C
authors.lastname: Daridon
authors.forename: Peter E
authors.initials: PE
authors.lastname: Lipsky
authors.forename: Thomas
authors.initials: T
authors.lastname: Dörner
mesh_terms: D000328:Adult; D016175:B-Lymphocyte Subsets / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D020029:Base Pairing / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology*; D002999:Clone Cells; D018985:Epitopes, B-Lymphocyte / Q000096:biosynthesis / Q000276:immunology*; D005260:Female; D015322:Gene Rearrangement, B-Lymphocyte / Q000235:genetics; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007156:Immunologic Memory / Q000235:genetics; D008297:Male; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism
chemical_list: D018985:Epitopes, B-Lymphocyte; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region