HOST IMMUNE SUPPRESSION AFTER SMALL-BOWEL LIVER-TRANSPLANTATION IN RATS

Simultaneous liver grafting in the Lewis (RT1(1))-to-DA (RT1a) rat str ain combination protects small intestinal grafts from rejection. The p resent study examined host immune responses after combined small bowel /liver transplantation (SBL) in this model. Orthotopic liver transplan tation and heterotopic small intestinal transplantation were performed simultaneously and compared with isolated small bowel allografts (SBA ) and isolated small bowel isografts (SBI). All rats were sacrificed o n postoperative day (POD) 7 or 14 for immunological and histological s tudies. The mean time to rejection of the SBA was 6.6 +/- 0.3 days. In contrast, there was no clinical or histological evidence of intestina l rejection in SBL recipients during the 14 days of follow-up. The SBL recipients showed clinical and histological evidence of graft-versus- host disease (GVHD). Lmphocyte proliferation and IL-2 production in re sponse to donor antigens were suppressed after SBL transplantation com pared with the SBA or the SBI controls (P < 0.05). Cell-mediated cytot oxicity and lymphocytotoxic antibody production against donor cells we re also significantly inhibited in the SBL recipients compared with th e SBA control group (P < 0.05). We conclude that SBL transplantation i n the Lewis-toDA rat strain combination: (1) suppresses host alloimmun e responses, (2) prevents early intestinal rejection, and (3) favors t he development of GVHD.