1. We studied the relation between immunopathology and progressive renal failure after nephrotoxic nephritis (NTN) in rats.
2. Thirty days after induction of nephritis by injection of rabbit anti-rat nephrotoxic serum, pairs of kidneys from 13 nephritic rats were transplanted into separate syngeneic recipients, one of whom had been pre-immunized with rabbit immunoglobulin G (IgG) whilst the other was naive.
3. Progression to renal failure of the transplanted nephritic kidney was studied after removal of the recipient's own kidneys; results from right and left kidney from a single donor in pre-immunized and naive recipients were compared.
4. There were substantial differences in autologous anti-rabbit IgG titres in naive and pre-immunized recipients; despite this pairs of kidneys from the same donor had almost identical courses as assessed by proteinuria, serum creatinine and graft survival.
5. There was substantial variation in survival of kidneys from different donors. But there were very strong correlations of graft survival with proteinuria (r = 0.97, t = 4.443, P<0.001) and reciprocal serum creatinine (r = 0.95, t = 4.32, P<0.001) in donors shortly before transplantation.
6. We conclude that autologous antibody titres did not influence the progression to renal failure after nephrotoxic nephritis. The rate of progression was already determined at the time of transplantation.