BACKGROUND: A major goal in clinical transplantation is the individualization of immunosuppression. This requires a definition of markers that identify patients at heightened risk of acute rejection and immune-mediated chronic allograft nephropathy. METHODS: Frequencies of interferon-gamma-producing donor-reactive cells were serially determined in unselected renal-transplant patients in an enzyme-linked immunosorbent spot assay (ELISPOT) before transplantation (n = 42) and up to 10 (mean 5.0) times during the first 6 months posttransplantation (n = 48) to determine detailed kinetics and analyze for correlation with acute rejection and graft function at 6 and 12 months posttransplantation. RESULTS: Pretransplant ELISPOT frequencies were significantly higher in patients with acute rejection (16/42) versus nonrejecters (26/42). Highly elevated pretransplant frequencies (>200 spots/300,000 peripheral blood mononuclear cells [PBMCs], n = 5/42) were associated with a risk of severe acute rejection episodes but were independent of risk factors such as high panel reactive antibodies. Early graft failure exclusively occurred in this group. Importantly, mean ELISPOT frequencies at weeks 2 and 3 but not at month 6 posttransplant correlated inversely with 6 and 12 months glomerular filtration rate. The correlation between ELISPOT frequencies and renal function showed the highest significance in patients without acute rejection. CONCLUSIONS: The pretransplant ELISPOT assay might be useful to identify T-cell presensitized patients, who are at heightened risk for severe early acute rejection. An analysis of ELISPOT donor-reactive cells during the early posttransplant period might allow an identification of patients at risk for immune-mediated graft deterioration.