title: CD21intCD23+follicular B cells express antigen-specific secretory IgM mRNA as primary and memory responses.
abstract: CD21intCD23+IgM+mouse follicular B cells comprise the bulk of the mature B-cell compartment, but it is not known whether these cells contribute to the humoral antibody response. We show using a direct RT-PCR method for antigen-specific VH, that FACS-sorted mouse CD21intCD23+B cells express specific secretory IgM VH transcripts in response to immunization and also exhibit a memory response. The secretory IgM expressed is distinct from the IgG expressed by cells of this phenotype, which we also analyse here, having a distinct broader distribution of CDR-H3 sequences and zero or low levels of somatic mutation in the region analysed. These results imply that cells of the CD21intCD23+phenotype have distinct IgM+and IgG+populations that contribute directly to the humoral antibody and memory responses by expressing antigen-specific secretory immunoglobulin. We also argue that the more diverse CDR-H3 sequences expressed by antigen-experienced IgM+CD21intCD23+follicular B cells would place them at the bottom of a recently hypothesized memory B-cell hierarchy.
authors.affiliation: Molecular Immunology Unit, Institute of Child Health, University College London, London, UK.
authors.forename: Qing-Hai
authors.initials: QH
authors.lastname: Meng
authors.affiliation: Department of Biosciences, University of Exeter, Exeter, UK.
authors.forename: Harry N
authors.identifier: 0000-0001-8186-7789
authors.initials: HN
authors.lastname: White
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D005260:Female; D007075:Immunoglobulin M / Q000235:genetics* / Q000276:immunology; D007156:Immunologic Memory / Q000235:genetics / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000235:genetics*; D017464:Receptors, Complement 3d / Q000276:immunology*; D017455:Receptors, IgE / Q000276:immunology*
chemical_list: D007075:Immunoglobulin M; D012333:RNA, Messenger; D017464:Receptors, Complement 3d; D017455:Receptors, IgE
keywords: B cells; follicular; memory; repertoire