To isolate and characterize monoclonal autoantibodies (Mab) directed to citrullinated antigens from patients with rheumatoid arthritis (RA).
Using lymphocytes from bone marrow or peripheral blood from RA patients, we constructed antibody fragment libraries representing the antibody repertoire of these individuals. Antibody fragments recognizing a citrulline-containing peptide were selected from these patient libraries. Individual antibody clones were analyzed for germline gene usage and reactivity toward citrullinated (auto)-antigens.
Sequence analysis of the cDNA encoding the 21 distinct antibody fragments that were obtained revealed a restricted germline gene usage. Individual antibody clones were positive in both antiperinuclear factor (APF) and antikeratin antibody (AKA) tests, stained citrullinated filaggrin and fibrinogen on Western blots, and reacted with subsets of citrulline-containing peptides in ELISA, but not with noncitrullinated peptides.
Our report describes the first recombinant human Mab fragments reactive with citrulline-containing peptides. The restricted germline gene usage of these antibodies, and the fact that the VH alleles used are not present in all individuals, may indicate the existence of a genetic predisposition for the development of anticitrulline antibodies in individuals with these germline alleles. The selected antibody clones may facilitate studies on the role of these autoantibodies and their target antigens in the development of RA.