Natural killer cell and alpha beta and gamma delta lymphocyte traffic intothe liver graft immediately after liver transplantation

Background. The persistence and migration of donor leukocytes has been well established, but cellular kinetics immediately after revascularization and the potential relevance of these different lymphocyte populations to spont aneous tolerance remain unclear. During the early hours of revascularizatio n, there is a transitory "congestion" of the liver graft, which is evidence of an early phase that we have termed "first cellular contact." Methods. We have carried out by flow cytometry a prospective comparative st udy of the peak kinetics of lymphocyte subpopulations contained in: (a) per ipheral blood and liver grafts at the time of multi-organ extraction from 1 4 brain-dead donors, (b) recipient peripheral blood before transplantation, and (c) recipient peripheral blood and liver grafts after (t=2 h) declampi ng and vascularization of the liver graft. Results. Before transplantation, the liver grafts contained large numbers o f natural killer (NK) and NK-like cells with early lymphocyte activation. I mmediately after revascularization, there was an influx of recipient NK and NK-like cells into the liver. Conclusions. NK and CD3(+)CD56(+) (NK-like) cells flooding into the liver g raft immediately after revascularization could rapidly destroy allogeneic c ells. However, spontaneous tolerance and the persistence of donor lymphocyt es after orthotopic liver transplant could be a result of donor TCR alpha b eta NK1.1 liver graft lymphocytes, which may be involved in the destruction of CD8(+) T lymphocytes that would have received the apoptosis signal, and to NK and NK-like cell inhibition via inhibitory NK receptors. The decreas e in gamma delta T lymphocytes in the two compartments suggests a mechanism of recirculation and capture in other lymphoid organs.