Replacement of donor lymphoid tissue in small-bowel transplants

Abstract

The presence of recipient lymphocytes in grafts is thought to equate with rejection. Thus, we wished to follow the fate of lymphocytes after transplant of the small bowel. Three complete small-bowel transplants, two with the liver from the same donor also transplanted, were done successfully. Patients were immunosuppressed with FK 506. 5 to 11% of lymphocytes in the recipients' peripheral blood were of donor origin during the early postoperative period when there were no clinical signs of graftversus-host disease. However, donor cells were no longer detectable after 12 to 54 days. Serial biopsy specimens of the grafted small bowel showed progressive replacement of lymphocytes in the lamina propria by those of the recipient's HLA phenotype. Lymphoid repopulation was complete after 10 to 12 weeks but the epithelial cells of the intestine remained those of the donor. The patients are on enteral alimentation after 5, 6, and 8 months with histopathologically normal or nearly normal intestines. Re-examination of assumptions about the rejection of intestinal grafts and strategies for its prevention are required following these observations.Little is known about the fate and function of lymphocytes in intestinal grafts, partly because long-term survival after transplant of the small intestine has been difficult to achieve. The first successful complete small-intestine transplant in man 1 was accomplished with continuous intravenous infusion of cyclosporin. The patient briefly had donor lymphocytes in peripheral blood during the early postoperative phase and at the same time had symptoms of graft-versushost disease (GVHD). We have followed the fate of host and donor lymphocytes in three patients treated with FK 506-one after small-bowel transplant and two after combined liverintestine grafting.Patient 1 lost the entire small bowel and most of the colon 5 months before transplant after a gun shot wound of the superior mesenteric artery; liver function was normal. Patients 2 and 3 had had total small-bowel resection several years earlier because of necrotising enterocolitis and thrombosis of the superior mesenteric artery, respectively, and both had liver failure following parenteral hyperalimentation. All grafts received arterial blood from the aorta, and intestinal venous outflow was through the liver of patient 1 or through the liver grafts of patients 2 and 3. FK 506 for immunosuppression was given intravenously at first (0·1 mg/kg per day) and later enterally (0·3 mg/kg per day in divided doses). Maintenance doses of FK 506 were lower. Prednisolone was given initially and later stopped (patients 2 and 3) or reduced (patient 1). Patients were maintained on intravenous nutrition for at least 2 months before starting jejunostomy and, ultimately, oral feeding. continuity restored, and patient 3 is still being fed through a nasogastric tube with its tip advanced into the graft jejunum.Peripheral blood lymphocytes were isolated with 'Ficoll-Hypaque' (Pharmacia LKB) and stored in liquid nitrogen until tested. Lymphoc...

Cell migration and chimerism after whole-organ transplantation: The basis of graft acceptance

“…The illusion of uniqueness of the hepatic graft was dispelled in 1991 with the demonstration, first in rat models (12) and then in human beings (13), that all successfully transplanted intestines also were chimeric. The epithelium of the bowel remained that of the donor, but lymphoid, dendritic and other leukocytes of recipient phenotype quickly became the dominant cells in the lamina propria, Peyer's patches and mesenteric nodes.…”

“…An additional crucial factor was the increasing sophistication of cell phenotyping techniques with which to differentiate donor from recipient cells in either experimental animals or human beings. For the first time, it was speculated in 1991 that graft chimerism might be a generic feature of all accepted grafts (13). This speculation soon was demonstrated with the kidney (14) and thoracic organs (15)(16)(17).…”

“…The vascular route by which cell migration occurred also was obvious in swine (48) and in human recipients of intestinal or liver-intestinal grafts (13,49). In the patients, donor cells in the early postoperative period accounted transiently for 5% to 15% of circulating mononuclear cells, usually without evidence of GVHD.…”

Cell migration, chimerism, and graft acceptance

“…13 Replaced donor lymphoid and dendritic cells spread through vascular routes to host lymphoid tissues, creating a state of mixed allogeneic chimerism-free of lethal or even clinically detectable graft-versus-host disease (GVHD) except in special strain combinations in which there is a poorly understood imbalance between the graft and recipient immune systems. 16,17 In addition, GVHD has been only a minor difficulty in human beings after cadaveric small bowel or multivisceral allotransplantation, 14,18,19 despite the use of histoincompatible donors and the routine development (as with the liver) of mixed allogeneic chimerism. Resistance to GVHD has also been described with mixed allogeneic or xenogeneic chimerism after bonemarrow transplantation.…”

“…The abundance of lymphoreticular cells in the liver and intestine, plus the development of phenotyping techniques, 8,14,22 have contributed to the discovery of cell migration and repopulation that follows organ transplantation. We believe that cell migration takes place to some degree with all successful transplantations, irrespective of the organ, with rapid seeding through the blood stream.…”