The Leu-1 B-cell subpopulation in patients with rheumatoid arthritis.

Ly-1-B cells have been shown to be elevated in autoimmune mice, especially NZB, and to secrete IgM autoantibody, suggesting that Ly-1 B cells may participate in autoimmune diseases. In this study, B-cell populations carrying Leu-1, a human T-cell surface molecule homologous to mouse Ly-1 (Leu-1 B), were examined by dual fluorescence flow cytometry, in peripheral blood lymphocytes taken from patients suffering from various autoimmune disease. These B cells were shown to be present at a significantly high percentage in rheumatoid arthritis (RA) patients. There was no significant correlation among the incidence of Leu-1 B cells, rheumatoid factor (RF) titers, and the amount of IgM production in vitro. There was, however, a significantly high incidence of Leu-1 B cells in RA patients with a high RF titer (greater than 5 X 2(13), suggesting that these B cells in RA may play an important role in IgM RF production in vivo.