To determine the frequency and repertoire of CD19+ B cells capable of producing antibodies reactive to type II collagen (CII) in synovial fluid (SF) and peripheral blood (PB) of patients with rheumatoid arthritis (RA) and PB of healthy control individuals.
CD19+ B cells were isolated and activated to secrete immunoglobulins (Ig) by CD4+ T cells. Frequencies of anti-CII B cells were determined by limiting dilution analysis. The isotype and cross-reactivity of the antibodies produced were determined by ELISA.
SF and PB from 5 patients and PB from 4 healthy controls were analyzed. Anti-CII CD19+ B cells were identified in all samples tested. In the RA SF, the percentage of activated B cells reactive to human CII was significantly higher than in the PB of patients with RA (p < 0.05) or controls (p < 0.01). A majority of anti-human CII B cells from patients' SF secreted IgG isotype, whereas most anti-human CII B cells in PB of patients and controls secreted IgM. The anti-CII B cells, regardless of source, are usually reactive to both native and denatured human CII, to different types of human collagens, and to type II collagens from different species.
Anti-CII CD19+ B cells responsive to activated helper T cells are present in both patients with RA and healthy individuals. However, these B cells, especially those secreting the IgG isotype, accumulate in the inflamed joints of RA patients.