Immunohistochemical analysis of the interstitial mast cells in rebiopsied patients with idiopathic mesangial proliferative glomerulonephritis.

Recent evidence suggests a role for mast cells in the pathogenesis of renal scarring in various glomerulopathies, therefore the present study was undertaken to evaluate whether mast cells have a role in tubulointerstitial fibrosis in rebiopsied patients with idiopathic mesangial proliferative glomerulonephritis (MPG) and to examine a possible relationship between mast cells and interstitial alpha-smooth muscle actin (alpha-SMA) expression as well as interstitial infiltrates. Seventeen patients with idiopathic mesangial proliferative glomerulonephritis, in whom renal biopsies were repeated and for whom light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available were examined quantitatively. Morphometric investigations were performed by means of a computer image analysis system. The study revealed that at the rebiopsy proteinuria was significantly lower as compared with the first biopsy. On the other hand, the mean values of the interstitial tryptase positive cells, expression of alpha-SMA, interstitial volume and CD68+ cells were at rebiopsy significantly increased. The mean values of CD45RB+, CD43+ and CD20+ cells did not differ significantly in these groups. In both initial biopsy and rebiopsy groups there were significant positive correlations between interstitial tryptase positive cells and interstitial expression of alpha-SMA, interstitial volume, and CD68+ cells. The present quantitative study may suggest that despite of the clinical improvement at rebiopsy, MPG is a progressive glomerular disease, and point to a role of mast cells in this process.