Regulatory T cells in alloreactivity after clinical heart transplantation

Purpose of review As the knowledge of CD4(+)CD25(bright+)FoxP3(+) regulatory T cells in experimental transplant models grows, we need to understand how and to what extent these suppressor cells regulate donor-directed immune events in the transplantation clinic. pp This review focuses on the function of regulatory T cells in the peripheral blood and the transplanted organ of patients after heart transplantation during immunological quiescence and rejection. Recent findings Here, we present data that peripheral CD4(+)CD25(bright+)FoxP3(+) T cells of heart transplant patients who experience acute rejection have inadequate immune regulatory function in vitro compared with those of nonrejecting patients. During rejection, potent donor-specific T-cell suppressors are present in the transplanted organ. Summary The studies in transplant patients' show that the function of CD4(+)CD25(bright+)FoxP3(+) regulatory T cells in alloimmunity is to inhibit the activation of effector T cells, to prevent rejection, and to control the antidonor response at the graft itself at later stages of immune reactivity.