title: Recruiting memory B cells with changed antigenic specificity.
abstract: During T cell-dependent antibody responses, the V region genes of responding B lymphocytes are physiologically mutated at a high rate. An intense selection process expands subclones of B cells producing mutant antibodies that bind Ag optimally. This implies that most mutant B cells and their antibody products are unselected and not often observed by conventional hybridoma or serum sampling procedures. Herein we show that the pool of mutant B cells includes unselected members that have acquired new antigenic specificities. Mice were immunized with a haptenated carrier protein to recruit and somatically diversity hapten-specific B cells producing antibodies with a defined V region bearing a major idiotype. During the primary immune response, the mice were given booster injections with a second related hapten conjugated to the same carrier. Hybridomas were isolated that produced idiotypic antibodies binding the second hapten but not the first. V gene sequencing analyses conclusively demonstrated that one of these was derived from a precursor B cell that expressed the defined unmutated V region with specificity for the first hapten. Sequence of the V genes expressed by the remaining six hybridomas supported this interpretation. In essence, single B cell clones were mutationally diversified to include members that had lost an original antigenic specificity while acquiring a new one, and the mutants were recruited into the memory compartment by antigenic selection. These results support the view that selection processes in vivo normally reveals only a small fraction of a mutationally diversified B cell clone. They also suggest a potential route by which antibodies of differing antigenic specificities can be generated from a single B cell clone of predefined origin and antigenic specificity.
authors.affiliation: Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver CO 80206.
authors.forename: J
authors.initials: J
authors.lastname: Ellenberger
authors.forename: G
authors.initials: G
authors.lastname: Creadon
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: L J
authors.initials: LJ
authors.lastname: Wysocki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D000939:Epitopes; D005803:Genes, Immunoglobulin; D006433:Hemocyanins / Q000276:immunology; D007114:Immunization; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007156:Immunologic Memory; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation
chemical_list: D000939:Epitopes; D007135:Immunoglobulin Variable Region; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin