Portal versus systemic delivery of insulin: Immunologic benefits for pancreas transplantation

Pancreas transplantation with portal venous drainage is gaining wide interest among pancreas transplantation centers primarily because of documented physiologic benefits. Of equal interest, however, is that pancreas transplantation with portal venous drainage mimics experimental animal models of portal tolerance. The interaction of immunomodulatory cells residing in the liver with donor antigen when it is introduced via the portal vein is being increasingly investigated. Certain subsets of lymphocytes, NK cells, and antigen-presenting cells have all been implicated. These data have encouraged clinicians to investigate possible immunologic benefits of portal venous drainage. Several investigators have now documented lower rejection rates when pancreas transplantations are portal venous drained compared with systemic venous drainage. In one study, this has even translated to improved early graft survival. Although some of these studies are hampered by small sample sizes, as more institutions adopt this technique, the clinical data should more clearly support the experimental evidence already present.