INCREASED DIMERIC IGA PRODUCING B-CELLS IN THE BONE-MARROW IN IGA NEPHROPATHY DETERMINED BY IN-SITU HYBRIDIZATION FOR J-CHAIN MESSENGER-RNA

Aim-To investigate the possible role of the systemic IgA immune system in the pathogenesis of IgA nephropathy. Methods-J chain mRNA expressi on in the IgA cells of the bone marrow was studied. Bone marrow trephi ne biopsy specimens from seven patients with IgA nephropathy and seven matched controls were examined by (1) non-isotopic in hybridisation ( ISH) and (2) combined immunofluorescence and non-isotopic ISH to ident ify the plasma cell type. Serum polymeric IgA was also determined usin g standard high pressure Liquid chromatography and sandwich enzyme lin ked immunosorbent assay. Results-Non-isotopic ISH revealed a similar n umber of J chain mRNA positive cells/unit length in biopsy specimens f rom patients (16.5 +/- 2.7 cells/mm) and controls (17.7 +/- 2.4 cells/ mm). Combined immunofluorescence and ISH revealed a greater proportion of J chain mRNA positive IgA cells in patients (7.6 +/- 1.45%) compar ed with controls (3 +/- 0.8%). Serum polymeric IgA was similar in both patients (91 +/- 22 mg/l) and controls (77 +/- 24 mg/l). Conclusion-T hese data suggest that excess production of dimeric IgA occurs in the bone marrow in IgA nephropathy.