title: Polyreactivity of human IgG Fc-binding phage antibodies constructed from synovial fluid CD38+ B cells of patients with rheumatoid arthritis.
abstract: Recent data indicate that rheumatoid factors (RFs) that occur in patients with rheumatoid arthritis (RA) are derived from Ig-producing terminally differentiated CD20-, CD38+ plasma cells present in synovial fluids (SFs). Phage antibody display libraries were constructed using CD38+ plasma cells isolated from SFs of two RF-seropositive RA patients. The libraries were enriched for phage antibodies (Phabs) binding to human IgG (HuIgG) Fc fragments and the sequences of their V genes were analysed. These data provided further evidence for an Ag-driven immune response in patients with RA, including expansion of clonally related B cells, selection and isotype switching, all hallmarks of a germinal center reaction. In the present study, the functional characteristics of these HuIgG Fc-binding monoclonal (mo) Phabs were further analysed in order to provide more insight into the specificity of HuIgG Fc-binding Phabs. Remarkably, all HuIgG Fc-binding moPhabs tested (n=48; derived from four different libraries) displayed polyreactivity. Structural analysis of the CDR3 regions revealed characteristic features of polyreactive Igs. Most H chain CDR3 regions harboured tryptophan/tyrosine-rich parts and approximately 60% of the L chain CDR3 regions of both RA patients displayed an identical stretch of amino acids (W/Y-D-S-S). Supportive for a dominant role of VH in specificity, exchange of VL regions with a single VH region yielded moPhabs with similar specificities. All together, the data suggest the presence of an Ag-driven process in the joints of patients with RA, including somatic mutation and clonal selection entailing isotype switching, resulting in the differentiation of B cells into polyreactive RF-secreting plasma cells.
authors.affiliation: Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: W J E
authors.initials: WJ
authors.lastname: van Esch
authors.forename: C C
authors.initials: CC
authors.lastname: Reparon-Schuijt
authors.forename: H J
authors.initials: HJ
authors.lastname: Hamstra
authors.forename: C
authors.initials: C
authors.lastname: van Kooten
authors.forename: T
authors.initials: T
authors.lastname: Logtenberg
authors.forename: F C
authors.initials: FC
authors.lastname: Breedveld
authors.forename: C L
authors.initials: CL
authors.lastname: Verweij
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000276:immunology; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001435:Bacteriophages / Q000276:immunology; D002919:Chymotrypsinogen / Q000276:immunology; D022801:Complementarity Determining Regions / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008562:Membrane Glycoproteins; D019151:Peptide Library; D011961:Receptors, Fc / Q000276:immunology; D012217:Rheumatoid Factor / Q000276:immunology*; D013582:Synovial Fluid / Q000276:immunology
chemical_list: D015703:Antigens, CD; D022801:Complementarity Determining Regions; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D019151:Peptide Library; D011961:Receptors, Fc; D012217:Rheumatoid Factor; D002919:Chymotrypsinogen; D036541:ADP-ribosyl Cyclase; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1