Monitoring of Cellular Immunity by Interferon-Gamma Enzyme-Linked Immunosorbent Spot Assay in Kidney Allograft Recipients: Preliminary Results of a Longitudinal Study

Several efforts have been made in past years to identify markers for patients at heightened risk of acute and chronic immune-mediated allograft rejection. The ex vivo monitoring of cellular immunity by the enzyme-linked immunosorbent spot (ELISPOT) assay has recently emerged as a primary tool in predicting short- and long-term outcomes in kidney allograft recipients. Therefore, we started the systematic application of interferon-gamma (IFN-γ) ELISPOT assay to measure the frequency of producing IFN-γ in recipient peripheral blood lymphocytes (PBLs) stimulated with donor lymphocytes before and 7, 14, 21, 28, and 60 days after transplantation. Preliminary results in eight kidney transplant patients indicated that the number of HLA mismatches never correlated with the number of IFN-γ spots. The frequencies of pretransplantation IFN-γ spots were positively and significantly correlated with the number of posttransplantation IFN-γ spots. Clinical outcomes were better among recipients with lower frequencies than those with higher frequencies of pre- and/or posttransplantation IFN-γ spots. The highest pre- and posttransplantation number of IFN-γ spots was observed in a patient who developed early acute rejection. Significant increases in the number of IFN-γ spots preceded the onset of acute rejection events and were decreased by supplemental IV steroid administration. Considering the low number of observations, these preliminary results must be considered cautiously; nevertheless, we are encouraged to extend the systematic application of serial IFN-γ ELISPOT assay measurements in a more consistent cohort of patients.