Collagen distribution in human membranous glomerulonephritis

In membranous glomerulonephritis (MGN), thickening of the glomerular basement membrane (GBM) is partly due to the accumulation of basement membrane material between and around immune deposits located on the epithelial aspect of the GBM. We investigated the distribution of type IV collagen chains (1/2, 3, 4, 5, 6) and of types I, III, V, and VI collagen in the glomeruli from 16 patients, by indirect immunofluorescence in 13 and the high-resolution immunogold technique in 6. No changes were detected in stage I MGN. The spiky projections of the GBM in stage II MGN and the basement membrane layers encircling immune deposits in stage III contained the 3, 4, and 5 chains of type IV collagen. In contrast, the 1/2 chains of type IV, as well as type VI collagen accumulated in the subendothelial aspect of the GBM. No significant staining for types I, III, and V collagens or for the 6 chain of type IV collagen was detected. The results show that, as in the normal glomeruli, the different chains of type IV collagen are not co-distributed in the glomerular extracellular matrix in MGN. They also indicate that type IV collagen chains and type VI collagen play an important role in the thickening of the GBM in human MGN.