Cold ischemia does not interfere with tolerance induction.

Background. Ischemia/reperfusion injury activates innate immunity, which in turn may prevent tolerance induction. We asked whether prolonged cold ischemia interferes with successful tolerance induction. Methods. Kidneys from Dark Agouti donors were grafted into binephrectomized Lewis rats after short (20 min) or prolonged (6 hr) cold ischemia. Tolerance was induced by nondepleting anti-CD4 monoclonal antibody RIB 5/2 (10 mg/kg for 5 days). Binephrectomized untreated and cytotoxic T-lymphocyte antigen (CTLA)-4Ig treated recipients served as controls. Animals were followed for 100 days. Adoptive transfer experiments into sublethally irradiated naive Lewis were performed at day 100. Animals received kidneys from Dark Agouti rats subsequently without further immunosuppression and were followed for an additional 20 days. Results. All RIB 5/2-treated recipients survived the first observation period independent of the cold ischemia time. Graft function, morphology, and transferred T-cell numbers were comparable in both groups. Twenty days after transfer amounts of intragraft and peripheral donor-derived cells were significantly reduced in recipients of the initially prolonged cold ischemia group associated with an attenuated immune response. Conclusions. Our results prove that an initially extended cold ischemia does not interfere with tolerance induced by RIB 5/2. Moreover, we conclude that a "tolerizing conditioning" achieved by prolonged cold ischemia during the tolerance-induction phase may reduce the immune response in recipients of an adoptive cell transfer.