Transfer of tolerance to heart and kidney allografts in the rat model.

Long-term allograft acceptance can be induced in the rat using a variety of maneuvers. One of the cardinal features of some models of tolerance is that once the tolerance state has been established, it can be perpetuated to naive recipients by the adoptive transfer of donor-specific regulatory cells. Such adoptive transfer studies have also addressed the capacity of T-cell subpopulations and non-T cells to transfer tolerance. However, tolerance cannot be transferred in all models. The underlying reasons for this are unclear with some studies pointing towards dose-dependent aspects and timing of expansion of T regulatory cells following tolerance transfer. Further exploration of this phenomenon will help us to understand better the mechanisms upon which allograft tolerance is based, and will provide new perspectives for further experimental studies.