Monocyte infiltration in human glomerulonephritis: alpha-1-antitrypsin as a marker for mononuclear phagocytes in renal biopsies.

Alpha-1-antitrypsin detected by immunoperoxidase has been used as a marker for infiltrating monocytes on formalin-fixed, paraffin-embedded sections of 75 renal biopsies. Patients were classified on the basis of glomerular hypercellularity on light microscopy. Monocytes increased with increasing glomerular hypercellularity, most being in diffuse proliferative GN (DPGN) and severe mesangiocapillary GN (MCGN-S). Monocytes were reduced by 48-95% in repeat biopsies of DPGN, mesangial proliferative GN and focal GN, but not in MCGN. In electron micrographs (70 biopsies) monocytes were identified but less frequently than by alpha-1-antitrypsin. Highest numbers were found with subepithelial or subendothelial deposits and lowest numbers in biopsies without deposits. The results show monocytes are detectable in human proliferative GN, numbers increasing with increasing glomerular hypercellularity, and subendothelial and subepithelial deposits.