title: Early onset of somatic mutation in immunoglobulin VH genes during the primary immune response.
abstract: The dynamics of somatic mutation in Ig variable genes was investigated in order to define a population of B cells undergoing mutation. BALB/cJ mice were injected with PC-KLH, and splenic RNA was prepared 5, 7, and 13 d later. The mRNA was annealed to gamma constant region primers to make cDNA transcripts encoding VH genes. 103 cDNA clones corresponding to 18 different genes from the VH7183, VH3660, and VHS107 subfamilies were sequenced to identify mutation. VH genes had a low level of mutation on day 5 after immunization and accumulated more mutation by day 7 at a rate of 10(-3) mutations per nucleotide per generation. However, by day 13, the number of mutations per gene did not increase, and most of the substitutions encoded replacement amino acid changes that were clustered in the hypervariable regions, indicating that the mutational process was less active during the second week and that antigen selection had occurred. The data are consistent with a developmentally regulated mechanism in which mutation is activated during the first week of the primary immune response for a limited time period, after which selection acts to preserve the beneficial mutants.
authors.affiliation: Department of Biochemistry, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
authors.forename: N S
authors.initials: NS
authors.lastname: Levy
authors.forename: U V
authors.initials: UV
authors.lastname: Malipiero
authors.forename: S G
authors.initials: SG
authors.lastname: Lebecque
authors.forename: P J
authors.initials: PJ
authors.lastname: Gearhart
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000032:analysis / Q000502:physiology; D001483:Base Sequence; D002999:Clone Cells / Q000502:physiology; D006433:Hemocyanins / Q000008:administration & dosage / Q000276:immunology; D006822:Hybrid Cells / Q000502:physiology*; D007074:Immunoglobulin G / Q000096:biosynthesis*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007700:Kinetics; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D010567:Pertussis Vaccine / Q000008:administration & dosage / Q000276:immunology; D013234:Stem Cells / Q000502:physiology
chemical_list: D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D010567:Pertussis Vaccine; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin