Panel of Reactive T Cells as a Measurement of Primed Cellular Alloimmunity in Kidney Transplant Candidates

Pretransplantation panel reactive antibody (PRA) testing assesses posttransplantation risk for antibody-mediated graft injury. It was postulated analogously that screening for effector/memory alloreactive T cells by "panel of reactive T cells" (PRT) using IFN-gamma enzyme-linked immunosorbent spot assays would evaluate independently cellular alloimmunity in transplant candidates. Peripheral blood lymphocytes from 41 hemodialysis patients who were awaiting first renal transplants were tested against a panel of allogeneic stimulator cells. Positive assays were defined arbitrarily as >25 spots/300,000 peripheral blood lymphocytes, and positive PRT was defined as when the responder reacted to 40 or 75% (PRT-75) of the stimulators. Seventeen percent of patients were PRT-75+, whereas 32% were PRA+. Twelve percent of the cohort was PRT-75+/PRA-, and only 5% of the patients were PRA+/PRT-75+, indicating that T cell alloreactivity did not routinely imply B cell sensitization and vice versa. PRT-75+ patients were more likely to be younger (<55 yr) and black. In contrast, a positive PRA was significantly associated with female gender but not race or age. Pretransplantation screening of cellular alloimmunity by enzyme-linked immunosorbent spot-based PRT detects a subset of hemodialysis patients who differ from those that are PRA+. Preliminary correlations with posttransplantation outcome in seven recipients suggest that PRT screening has the potential to aid in risk assessment in renal transplant candidates.