Increase of peripheral blood B cells with Fc receptor for IgA in patients with IgA nephropathy.

A B-cell subset with Fc receptors for IgA (B alpha cells) has been observed in human peripheral blood. To investigate aberrations of B cells in a diseased state, the percentages of B alpha cells were enumerated in peripheral blood from patients with IgA nephropathy, which is characterized by preponderant deposition of IgA-dominant immune complexes in the glomerular mesangial area. The present study showed a significant increase in B alpha cells in peripheral blood from patients with IgA nephropathy but not in those with chronic proliferative glomerulonephritis without mesangial IgA deposition. Most Fc alpha R-bearing cells were observed in surface IgA bearing lymphocytes. No linear correlation was observed between the levels of serum IgA and the percentages of B alpha cells. The addition of aggregated IgA to cultures did not induce Fc alpha R-bearing B cells in vitro. It is postulated that B alpha cells might have some pathogenetic role in the development of IgA nephropathy and that some antigenic stimuli might play a role in the increase of peripheral blood B alpha cells in patients with IgA nephropathy.