Kinetic, affinity, and diversity limits of human polyclonal antibody responses against tetanus toxoid.
Due to technical limitations, little knowledge exists on the composition of Ag-specific polyclonal Ab responses. Hence, we here present a molecular analysis of two representative human Ab repertoires isolated by using a novel single-cell cloning approach. The observed genetic diversity among tetanus toxoid-specific plasma cells indicate that human polyclonal repertoires are limited to the order of 100 B cell clones and hypermutated variants thereof. Affinity and kinetic binding constants are log-normally distributed, and median values are close to the proposed affinity ceilings for positive selection. Abs varied a million-fold in affinity but were restricted in their off-rates with an upper limit of 2 x 10(-3) s(-1). Identification of Abs of high affinity without hypermutations in combination with a modest effect of hypermutations on observed affinity increases indicate that Abs selected from the naive repertoire are not only of low affinity but cover a relatively large span in affinity, reaching into the subnanomolar range.
Poulsen
Tine Rugh
TR
Department for Antibody Discovery, Symphogen A/S, Lyngby, Denmark.
Meijer
Per-Johan
PJ
Jensen
Allan
A
Nielsen
Lars S
LS
Andersen
Peter S
PS
D000328:Adult; D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000235:genetics; D000915:Antibody Affinity / Q000235:genetics; D000916:Antibody Diversity / Q000235:genetics; D003017:Clostridium tetani / Q000276:immunology; D022801:Complementarity Determining Regions / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D006801:Humans; D007133:Immunoglobulin Joining Region / Q000096:biosynthesis / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000096:biosynthesis / Q000235:genetics; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013745:Tetanus Toxoid / Q000276:immunology* / Q000378:metabolism