Immunohistochemical analysis of human serum sickness glomerulonephritis

To analyze pathological and immunohistochemical characteristics of glomerulonephritis in human serum sickness.

Renal biopsy specimens from two female patients with serum sickness that ensued after application of anti-lymphocyte horse globulin for aplastic anemia were analyzed by light microscopy, immunofluorescence, and electron microscopy. To prove the depositions of foreign protein, frozen sections were incubated with fluorescein-conjugated anti-horse protein serum. Immunohistochemical analysis was performed on B5-fixed paraplast-embedded tissue or frozen acetone-fixed sections with the primary antibodies for molecules/cell markers CD35, CD43, CD45RO, CD68, CD2, lysozime, L26, and S100.

Diffuse proliferating and necrotizing glomerulonephritis with crescents was found. There were coarse granular mesangial, subepithelial, subendothelial, and intramembranaceous deposits of mainly horse globulin, C3, and IgG. Most mesangium infiltrating cells were macrophages and T-lymphocytes. Electron microscopy revealed hypertrophy of podocytes, but immunohistochemistry did not show their normal CD35 (C3b-receptor) staining. Apart from epithelial cells, main crescent forming cells were macrophages and T-lymphocytes. Rare dendritic cells and abundant infiltration of macrophages, T-lymphocytes, and neutrophiles were found in the interstitium.

In severe serum sickness, glomeruli and tubuli are destroyed beyond the range usually seen in other types of glomerulonephritis caused by immune complexes, except in cases with widespread crescents. Hypertrophy of podocytes and loss of their normal C3b-receptor staining has not yet been described in the literature. C3b-receptors on podocytes could play a role in pathogenesis of glomerular injury caused by immune complexes.