INCREASED IMMUNOGLOBULIN-A AND IMMUNOGLOBULIN A(1) CELLS IN BONE-MARROW TREPHINE BIOPSY SPECIMENS IN IMMUNOGLOBULIN-A NEPHROPATHY

The origin of mesangial immunoglobulin A (IgA) in IgA nephropathy remains unknown. To investigate potential abnormalities within the bone marrow in this condition, bone marrow trephine biopsy specimens from seven patients and matched controls were studied using two-color immunofluorescence. In addition, serum levels of IgA and IgA(1) were determined by radial immunodiffusion. Serum levels of IgA and IgA(1) were higher in patients than in controls (4.53 +/- 1.38 g/L v 2.56 +/- 1 g/L, P < 0.01 and 3.68 +/- 1.11 g/L v 1.92 +/- 0.7 g/L, P < 0.005, respectively). In addition, patient trephine biopsy specimens contained an increased percentage of IgA plasma cells (61.6% +/- 4.4%) compared with controls (47.3% +/- 2.5%) (P < 0.02). The proportion of IgA plasma cells bearing subclass IgA(1) was also greater in the patient biopsy specimens (91.6% +/- 1.9%) compared with controls (81.4% +/- 2.7%) (P < 0.01). In patients a positive correlation between the percentage of marrow IgA plasma cells and serum IgA levels was found (r = 0.94, P < 0.002). However, our studies failed to demonstrate a similar correlation between serum IgA(1) levels and IgA(1) marrow cells. These findings support the hypothesis that mesangial IgA may derive from the bone marrow. (C) 1994 by the National Kidney Foundation, Inc.