Failure of cyclosporine to prevent small bowel allograft rejection in pigs

The effect of cyclosporine (CyS) on survival and function of 250 cm intraabdominal heterotopic small bowel allografts was studied in outbred pigs. Experimental animals received oral CyS alone (25 mg/kg/day), or oral CyS, donor bowel radiation, and recipient splenectomy; controls were untreated. Excluding technical failures, no significant differences in graft survival were observed, although one relatively long-term survivor occurred in each treated group. Rejection was not related to cyclosporine levels. These data show that CyS as a single agent as well as when used with supplemental therapy does not uniformly prevent rejection of small bowel allografts in pigs, although an occasional long-term survivor will occur. The failure to achieve consistently successful engraftment may reflect the large quantity of lymphoid tissue in small bowel. Further experimentation is required before human transplantation is again attempted.