PERSISTENCE OF DONOR LYMPHOCYTES IN LIVER ALLOGRAFT RECIPIENTS

Occasional cases of graft-versus-host disease after liver transplantat ion indicate a transfer of donor lymphocytes by human liver grafts. Ho wever, little is known about the usual fate and potential function of passenger lymphocytes in clinical liver transplantation. In this study , we have analyzed liver graft recipients for the presence of donor ly mphocytes in the early course after transplantation. The presence of s uch cells in blood, the graft, and, occasionally, the skin was studied by the use of mAb to polymorphic HLA class I determinants and double- staining techniques in flow cytometry and immunocytology. The findings were compared with the clinical courses and with the results of routi ne graft biopsies. Within the first week after transplantation, in all 16 patients, between 1% and 24% donor lymphocytes (T, NK, and B cells ) were detectable in blood, and in 14 of 22 patients (64%), between 2% and 23% donor T cells were found in the graft. After more than 2 week s, donor cells were still present in blood in 2 of 14 patients at very low numbers. The presence of donor lymphocytes in the graft was assoc iated with intragraft immune activation in 5 of 15 patients, but no cl inical rejection occurred in these cases; mild graft-versus-host disea se was observed in one patient. These findings demonstrate that donor lymphocytes regularly persist in liver-grafted patients for some time; this transient mixed lymphoid chimerism is only rarely associated wit h clinical graft-versus-host disease and some evidence even suggests t hat these donor-derived lymphocytes may exert beneficial immunomodulat ory properties.