Mast cells in rapidly progressive glomerulonephritis

The role of mast cells (MC) in tubulointerstitial damage in glomerulonephri tis (CN) is not fully understood. The distribution of MC was compared in re nal biopsies from 50 patients with different stages of rapidly progressive GN (RPGN) and in 20 control samples. The immunoreactivity of renal MC with anti-tryptase and anti-chymase antibodies was studied. Interstitial myofibr oblasts were stained with anti-alpha-smooth muscle actin (alpha-SMA) antibo dy, and inflammatory cells were identified by anti-CD3, -CD20, and -CD68 mo noclonal antibodies. Positively stained cells were counted, and the relativ e interstitial and fractional areas of anti-alpha-SMA-stained cells were me asured. MC were rarely found in control samples. In contrast, samples showi ng crescentic GN contained numerous tryptase-positive MC (MCT) (43.7 +/- 4. 65 versus 7.14 +/- 1.3/mm(2)) and fewer tryptase- and chymase-positive MC ( MCTC) (13.8 +/- 1.86 versus 1.89 +/- 0.86/mm(2)) in the renal interstitium but never in the glomerulus. Double immunostaining demonstrated the presenc e of both phenotypes of MC. Accumulation of MC was significantly correlated with the numbers elf T lymphocytes (MCT, r = 0.67) and interstitial macrop hages (MCT, r = 0.455). There was also a significant correlation between th e number of MCT and the relative interstitial area. The number of MCTC was well correlated with the fractional area of alpha-SMA-positive interstitium (r = 0.749) and the percentage of the interstitial fibrotic area (r = 0.59 8). There was also a significant negative correlation between interstitial MG(TC) accumulation and creatinine clearance (r = 0.661). The density of MC TC was higher (1.4-fold) in advanced forms of GN associated with fibrocellu lar crescents and interstitial fibrosis. These results show the potential i nvolvement of MC in the fibroproliferative process in the renal interstitiu m of patients with RPGN. The results indicate that these cells constitute p art of the overall inflammatory cell accumulation in RPGN.