Immunofluorescence, light and electron microscopic examinations were carried out to clarify the relations between the progression of glomerular lesion and the changes in the amount and distribution of glomerular proteins, such as 7S and non-collagenous (NC-1) domain of Type IV collagens, laminin (LN), and fibronectin (FN), and of IgA deposits in patients with IgA nephropathy. The intensity and distribution of these extracellular proteins were similar between the glomeruli from normal individuals and patients with IgA nephropathy at stages of “minimal” to “slight” lesions. In “moderate” to “advanced” stages of IgA nephropathy, the amount of FN, which is normally distributed only in the glomerular mesangium, was increased in the mesangium with FN being observed along the glomerular capillary walls. An increase in the amount of 7S domain of Type IV collagen and LN was also observed mainly in the subendothelial portions of the diseased glomerular capillary walls, and to a lesser extent in the mesangial areas. The NC-1 domain of Type IV collagen and glomerular basement membrane (GBM) substance, detected by serum autoantibodies from patients with Goodpasture's syndrome, did not show any changes and were distributed only along the GBM in IgA nephropathy as in normal subjects. It appeared that Type IV collagen, LN and FN detected in the glomeruli were not associated with IgA deposits in IgA nephropathy as determined by double immunofluorescence and acid-buffer elution studies. In conclusion, hyperproduction of these extracellular matrix proteins mainly in the glomerular mesangium is closely related to the progression of glomerular lesions in patients with IgA nephropathy.
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