Recipient CD8+ cells are responsible for the rapid elimination of allogeneic donor lymphoid cells.

Blood transfusion can result in a variety of immunologic responses, including alloimmunization, transfusion-associated graft-versus-host disease, and immunosuppression that results in increased postoperative infection rate, and can also result in increased survival of allografts. One of the many factors influencing the resulting immunologic responses from a blood transfusion is the persistence of the donor leukocytes. A recent study has shown that almost all (99.9%) allogeneic leukocytes are removed within 2 days following transfusion but did not characterize the mechanism responsible for the rapid removal of allogeneic donor cells. Using a murine model these studies show that it is recipient CD8+ T cells that are responsible for the rapid elimination of allogeneic lymphocytes in naive recipients. Effective elimination was dependent on the donor/recipient combination and required that the donor cells express at least one MHC class I disparity to be recognized by the recipient CD8+ cells and that the donor cells also be able to induce additional responses that were needed by the CD8+ cells to manifest full activity. The perforin pathway was the predominant pathway used by the recipient CD8+ cells to mediate this elimination.