Expression of Fas antigen and Bcl-2 in human glomerulonephritis

To understand the regulatory mechanism of apoptosis in human glomerulonephritis, we examined the expression of Fas antigen (CD95) and Bcl-2 in five normal human kidney specimens and 80 tissues from patients with several types of glomerular diseases. These proteins were detected in glomeruli by immunofluorescence. The number of intraglomerular cells positive for Fas antigen was high in Henoch-Schönlein purpura nephritis and lupus nephritis, and that of Bcl-2-positive intraglomerular cells was high in lupus nephritis, focal glomerular sclerosis, and IgA nephritis. Dual-labeling and staining on serial sections indicated that mesangial cells and occasionally infiltrating leukocytes expressed Fas antigen and Bcl-2. In situ hybridization detected Bcl-2 mRNA in glomerular cells. Electron microscopy revealed apoptotic cells and apoptotic bodies in proliferated mesangial areas and within the glomerular capillaries. Fragmented DNA was detected in glomeruli by in situ nick end labeling, the data of which paralleled the number of Fas antigen-positive intraglomerular cells. In mesangial proliferative types of glomerulonephritis, the population of Bcl-2-positive intraglomerular cells, but not that of Fas antigen-positive cells, was significantly correlated with the number of proliferating cell nuclear antigen-positive glomerular cells, the grade of mesangial cell increase, and the magnitude of proteinuria. This study showed that Fas antigen and Bcl-2 are up-regulated in the glomeruli of several types of human renal diseases. Bcl-2 overexpression might play a role in the prolonged proliferation of mesangial cells and glomerular hypercellularity in glomerulonephritis.