Fig. 2.

Viral infections interfere with the induction of tolerance against allo-antigens. (A) Naïve allo-specific T cells (colored grey) are deleted and become functionally anergic (colored green) after receiving a transfusion of donor allogeneic cells (donor-specific transfusion or DST) with a co-stimulatory blockade. Mice that have been tolerized to the allo-antigens can then accept allogeneic skin grafts. (B) A viral infection during the co-stimulatory blockade protocol will activate allo-specific T cells (colored yellow) and interfere with the establishment of tolerance, resulting in skin graft rejection. (C) Naïve mice infected with viruses generate memory allo-specific T cells (colored blue) that are refractory to the induction of tolerance using co-stimulatory blockade protocols and reject allogeneic skin grafts.