The increased expression of CD21 on AchR specified B cells in patients with myasthenia gravis.

CD21, a major complement receptor expressed on B cells, is associated with autoimmune disorders. In the present study, we investigated the role of CD21 in pathogenesis of myasthenia gravis (MG) in relationship to anti-acetylcholine receptor (AchR) IgG (anti-AchR IgG) secretion. We detected increased surface expression of CD21 on AchR specified B cells as well as decreased surface expression of CD21 on total B cells in peripheral blood of patients with generalized MG (gMG). In addition, the serum concentrations of soluble secreted CD21 (sCD21) were decreased in patients with gMG. We also found that the level of CD21(+) AchR specified B cells correlated positively with serum anti-AchR IgG level, while the serum concentration of soluble CD21 correlated negatively with serum anti-AchR IgG level. Our data suggests that CD21 might facilitate its function on AchR specified B cell activation, resulting in the secretion of anti-AchR IgG.