BCR and rheumatoid arthritis: This study was designed to investigate the distribution of the B-cell receptor (BCR) repertoire using a high-throughput quantitative approach in a unique cohort of 11 RA patients, in which synovial tissue (ST) biopsies were taken from multiple locations within the same joint, in another (contralateral) joint, as well as synovial fluid (SF) and peripheral blood (PB) samples.