Characterization and quantification of proliferating cell patterns in endocapillary proliferation

Endocapillary proliferation (EP) is a common pathological finding in proliferative glomerulonephritis (GN). Its appearance indicates the presence of active lesions of GN. In this study, we reinvestigated the pathological features of EP. Cell markers that included CD15, CD68, CD45RO, CD31 and alpha-smooth muscle actin (alpha-SMA) were used to identify the intraglomerular cells in renal biopsy tissues collected from patients with post-streptococcal acute GN (PSAGN), methicillin-resistant Staphylococcus aureus-associated GN (MRSAGN) with or without EP, membranoproliferative GN (MPGN) with or without EP, Henoch-Schnlein nephritis, immunoglobulin A nephropathy, membranous nephropathy and minimal change nephrotic syndrome. Proliferating cells and apoptotic cells were investigated simultaneously. The glomerular infiltrating polymorphonuclear leukocytes, macrophages, T cells, mesangial cells and endothelial cells were enumerated. In PSAGN, the glomerulus was enlarged and all cell types were greatly increased. In MRSAGN EP, the glomerulus was slightly enlarged with abundant infiltrating leukocytes and monocyte/macrophages and had moderate mesangial cell proliferation with negligible endothelial cell proliferation. In MPGN, the glomerulus markedly enlarged with multiple monocyte/macrophages and remarkable mesangial proliferation. The mesangial cells in EP glomeruli were highly activated as evidenced by alpha-SMA expression, particularly in PSAGN. This is the first report to use monoclonal antibodies specific for cell markers to quantitatively analyze and compare the proliferating cell types in EP glomeruli in different forms of GN. The results suggest that identification of the presence of polymorphonuclear leukocytes in the capillary lumen might help in differentiating between glomerular global and segmental EP.