CHARACTERIZATION OF HEPATIC ALLOGRAFT INFILTRATES IN RATS PRETREATED WITH DONOR-SPECIFIC BLOOD-TRANSFUSION (DST)

A single intravenous injection of 1 ml freshly heparinized donor blood given 7 days prior to transplantation prolonged significantly the sur vival of subsequent hepatic allografts in fully allogeneic ACI(RT1(a)) -to-LEW(RT1(1)) rats. The cellular identity of allograft infiltrates w as investigated at various times after transplantation using OX8 (CD8) and W3/25 (CD4) monoclonal antibodies. The number of CD8(+) cells inc reased rapidly and reached a peak on Day 3 after transplantation of th e untreated allografts. Similarly, the number of CD8(+) cells in the a llografts from DST-treated rats was maximum on Day 3 and decreased gra dually thereafter. The maximum number of CD4(+) cells was found on Day 3 in untreated allografts. In contrast, no significant infiltration o f CD4(+) cells occurred during the first 7 days after transplantation in DST-treated allografts. Thereafter, the number of CD4(+) cells incr eased rapidly and reached a peak on Day 14. CD4(+) cells remained pers istently elevated in hepatic allografts of rats pretreated with DST, b ut did not become functionally competent or initiate rejection. These findings suggest that persistent infiltration by CD4(+) cells is a cha racteristic feature of long-surviving hepatic allografts in rats pretr eated with DST. (C) 1995 Academic Press, Inc.