PHAGOCYTOSIS BY GLOMERULAR ENDOTHELIAL-CELLS IN INFECTION-RELATED GLOMERULOPATHY

Glomerulonephritis in BALB/c mice following infection with Trypanosoma brucei is characterized by albuminuria and glomerular deposition of i mmunoglobulins. Electron-dense deposits are present in the mesangium, as well as subendothelially and subepithelially along the glomerular c apillary wall. In this study the nature of intracytoplasmic, electron- dense, round structures observed in glomerular endothelial cells was i nvestigated by immunoelectron-microscopy and enzyme histochemistry. Th e presence of these structures was related in time with the developmen t of proteinuria. Mice from the C57BL10 strain, which upon infection d evelop glomerular immune complexes without proteinuria, were examined as well. The results demonstrated that the first endothelial changes, occurring 3-4 weeks after infection, were swelling of endothelial cell s containing intracytoplasmic, electron-dense, round structures. These changes were seen prior to the onset of proteinuria, and were not pre sent in glomeruli of mice that did not develop proteinuria. The endoth elial granules were shown to contain immunoglobulins and typical lysos omal enzymes, providing evidence for phagocytosis by the glomerular en dothelial cells. Liver endothelial cells did not show comparable chang es. Thus, local phagocytosis by glomerular endothelial cells is shown to be a specific event in the development of glomerular disease.