The role of the immune system in the progression of experimental nephrotoxic serum nephritis (NTN) in rats has been evaluated. Proteinuria and renal functional impairment during the sub-acute phase of the disease determined the long-term prognosis of the nephritis regardless of the humoral autologous antibody levels. In contrast to the acute, immune mediated glomerulonephritis, chronic glomerular scarring in NTN proceeds independently of the host immune response.