Role for CD4+CD25+ T Cells in Inhibition of Graft Rejection by Extracorporeal Photopheresis

ECP extends graft survival even in fully histoincompatible strain combinations with no immunosuppression. It increases the frequency of FoxP3+CD4+CD25+ splenic T cells, and its effects can be transferred to untreated recipients using minimal numbers of CD4+CD25+ T cells, indicating that CD4+CD25+ T cells may play a key role in the immunomodulatory effects of ECP.