title: Specificity and idiotope expression of IgM produced by CD5+ and CD5- cord blood B-cell clones.
abstract: Epstein-Barr virus (EBV)-immortalized monoclonal B-cell lines were established from CD5+ and CD5- cord-blood B cells. IgM from many of both CD5+ and CD5- clones reacted with IgG-Fc, ssDNA, and a variety of other autoantigens. More CD5+ B cells that used light chains of the kappa isotype reacted with IgG-Fc and ssDNA than kappa-bearing CD5- B cells. Because many of the clones reacted with IgG-Fc, they were analyzed for the expression of cross-reactive idiotypes (CRI) associated with rheumatoid factor and cold agglutinin paraproteins using murine antibodies (mAb) recognizing V kappa and VH subgroup-associated determinants. Expression of the V kappa IIIb sub-subgroup-associated idiotope recognized by 17.109 mAb was expressed at significantly higher frequency (32%; p less than 0.05) and IgM antibodies derived from the CD5+ compared with the CD5- clones (5%). Both CD5+ and CD5- clones expressed the RF paraprotein-associated idiotope recognized by G8 mAb to the same extent. Similar results were obtained using binding to SpA as a marker of VH III family usage. Furthermore, no differences in frequency of expression of RF paraprotein-associated idiotopes recognized by B6 and/or D12, and characteristic of some antibodies using VH III family genes, were found between the CD5+ and CD5- populations. Although a higher than expected frequency of VH IV-gene expression was demonstrated (around 30%) in both CD5+ and CD5- cells, there were differences in expression of CRI recognized by mAb Lc1 and R2.1A2 with specificities for two VH IV subfamilies. While some CD5+ and CD5- clones were identified in which their IgM reacted with mAb Lc1, only CD5+ clones were recognized by another mAb R2.1A2. Analysis of the relationships between antigen specificities and V kappa- and VH-family gene usage indicated that auto- or polyreactivity was not associated with V kappa III nor any particular VH family. The higher frequency of the V kappa IIIb sub-subgroup-associated idiotope recognized by 17-109 in the CD5+ clones and the association of CD5+ B cells with the VH IV subfamily recognized by mAb R2.1A2 and 9G4 may suggest that CD5+ B cells in cord blood are expanded as a result of recruitment within the fetal environment.
authors.affiliation: Department of Immunology, University College and Middlesex School of Medicine, London, United Kingdom.
authors.forename: P M
authors.initials: PM
authors.lastname: Lydyard
authors.forename: L E
authors.initials: LE
authors.lastname: MacKenzie
authors.forename: P Y
authors.initials: PY
authors.lastname: Youinou
authors.forename: M
authors.initials: M
authors.lastname: Deane
authors.forename: R
authors.initials: R
authors.lastname: Jefferis
authors.forename: R A
authors.initials: RA
authors.lastname: Mageed
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D018956:CD5 Antigens; D002999:Clone Cells; D005312:Fetal Blood / Q000276:immunology*; D015870:Gene Expression; D005803:Genes, Immunoglobulin; D004854:Herpesvirus 4, Human / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007130:Immunoglobulin Idiotypes / Q000235:genetics*; D007075:Immunoglobulin M / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice; D005810:Multigene Family
chemical_list: D015703:Antigens, CD; D018956:CD5 Antigens; D007143:Immunoglobulin Heavy Chains; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D007135:Immunoglobulin Variable Region