title: The genetic basis of human VH4 gene family-associated cross-reactive idiotype expression in CD5+ and CD5- cord blood B-lymphocyte clones.
abstract: In a recent study we have observed a high frequency expression of cross-reactive idiotypes encoded by genes from the relatively small VH4 family of immunoglobulin heavy chain genes in cord blood B-lymphocyte lines. Furthermore, we have demonstrated a selective pattern of expression of two VH4-associated cross-reactive idiotype (CRI) in B-lymphocyte lines established from CD5+ and CD5- cord blood B-lymphocytes. There was a restricted expression of one CRI marker recognized by the 9G4 monoclonal antibody in lines established from CD5+ B-lymphocytes but not in those established from the CD5- population. In the current study we examine the molecular basis for the selective pattern of CRI expression. Nucleotide-sequence analysis of functional immunoglobulin heavy chain (IgH) gene rearrangements in three CD5+ lines expressing the CRI recognised by 9G4 reveal that all use a single gene from the VH4 family, the V4.21 gene. However, all three lines have distinct third complementarity determining regions (CDR3) implying different clonal origins. In contrast, four cord blood cell lines (two established from CD5+ B-lymphocytes) expressing the CRI recognized by MoAb Lc1 have functional IgH gene rearrangements involving two different genes from the VH4 family, the V71-4, and V2-1 genes. Antigen specificity analysis reveals that all three 9G4-reactive lines produce antibodies that react with the I and/or i red blood cell carbohydrate antigens. These data suggest that the distinction in VH4 gene use in CD5+ B-lymphocytes in cord blood results from a selection process in vivo that shapes the repertoire of CD5+ B-lymphocytes. This study extends recent observations that the monoclonal anti-CRI antibodies 9G4 and Lc1 are markers of two distinct subgroups of proteins encoded by two subsets of genes within the VH4 family. Furthermore, it appears that amino acid residues in framework region one and complementarity determining region two are critical for the expression of the cross reactive idiotypes and the serological distinction between the two subgroups of proteins.
authors.affiliation: Department of Hematology, Royal Free Hospital, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Deane
authors.forename: L E
authors.initials: LE
authors.lastname: Mackenzie
authors.forename: F K
authors.initials: FK
authors.lastname: Stevenson
authors.forename: P Y
authors.initials: PY
authors.lastname: Youinou
authors.forename: P M
authors.initials: PM
authors.lastname: Lydyard
authors.forename: R A
authors.initials: RA
authors.lastname: Mageed
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D018956:CD5 Antigens; D002460:Cell Line; D002999:Clone Cells; D003429:Cross Reactions; D005312:Fetal Blood / Q000276:immunology; D005434:Flow Cytometry; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain / Q000235:genetics / Q000276:immunology; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology; D007130:Immunoglobulin Idiotypes / Q000276:immunology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018956:CD5 Antigens; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes