Participation of monocytes in glomerulonephritis in acute serum sickness of rabbit

Acute serum sickness in the rabbit was studied with special reference to the role of monocytes in the inflammatory process in the glomerulus. It was revealed that macrophages were the major factor in producing glomerular hypercellularity in acute serum sickness. Proliferation of intrinsic glomerular cells or accumulation of polymorphonuclear leukocytes (PMNs) was minimal. Ultrastructural characteristics of these phagocytic cells were described. Macrophages engulfed various inflammatory products such as fibrin and cell debri in the glomerular capillary. Colloidal carbon administered at the active inflammatory stage was found to be mostly engulfed by macrophages, little by mesangial cells, and was not seen in endothelial or epithelial cells and PMNs. The selective ingestion of the carbon particles by these macrophages made it possible to differentiate them from glomerular cells. This in turn indicated that the macrophages were derived from neither endothelial nor menangial cells and that they were of blood monocytic origin. It was suggested that monocytic cells participated in glomerular inflammation but they, on the other hand, contributed to the repair of glomerular injuries through their active role for phagocytosis.