Accelerated serum sickness in the rabbit. II. Glomerular ultrastructural lesions in transient proliferative and progressive disorganizing glomerulonephritis.

Electron microscopic analysis was performed on the development of irreversible glomerular distortion in experimental serum sickness nephritis in the rabbit. In the animals showing transient albuminuria, glomerular hypercellularity was due to the accumulation of monocytes and polymorphonuclear leukocytes and was seen to recover to nearly normal glomerulus. In this condition the glomerular structure was observed to be well preserved throughout the inflammation. In contrast, in the animals showing persistent proteinnuria, a disorganizing process was found in their glomeruli. Mesangial disintegration resulted in collapsed scarring or circumferential mesangial interposition of the glomeruli. Extracapillary exudation, sometimes with the rupture of the glomerular basement membrane, was often associated with granulomatous glomerular lesions or cresent formation. The results showed that the structural disintegration is a fundamental event in the development of progressive glomerulonephritis.