One-way MLR revealed a critical role of donor-specific FoxP3⁺ Tregs for the maintenance of tolerance.

<p>Baseline levels were assessed when naïve Lewis splenic cells were used as responders. Hyporeactivity to donor antigen stimulation and immunocompetence for third-party antigens stimulation (ACI rats) in recipients of group 5 at POD 100 was demonstrated. When donor-specific FoxP3⁺ Tregs were depleted from the responder populations, robust antidonor alloreactivity reappeared.