Type 1 diabetes is the result of a selective destruction of pancreatic islets by autoreactive T-cells. Therefore, in the contest of islet or pancreas transplantation, newly transplanted p-cells are threatened by both recurrent autoimmune and alloimmune responses in recipients with type 1 diabetes. In the present study using spontaneously diabetic BE rats, we demonstrate that whereas isolated islets are susceptible to autoimmune recurrence and rejection, pancreaticoduodenal grafts are resistant to these biological processes. This resistance is mediated by lymphohematopoietic cells transplanted with the graft, since inactivation of these passenger cells by irradiation uniformly rendered the pancreaticoduodenal grafts susceptible to recurrent autoimmunity We further studied the impact of local immunomodulation on autoimmune recurrence and rejection by ex vivo adenovirus-mediated CTLA4Ig gene transfer to pancreaticoduodenal grafts. Syngeneic DR-BE pancreaticoduodenal grafts transduced with AdmCTLA4Ig were rescued from recurrent autoimmunity: La fully histoincompatible LEW-->BB transplants, in which rejection and recurrence should be able to act synergistically; AdmCTLA4Ig transduced LEW-pancreaticoduodenal allografts enjoyed markedly prolonged survival in diabetic BE recipients. Ln situ reverse transcription-polymerase chain reaction revealed that transferred CTLA4Ig gene was strongly expressed in both endocrine and exocrine tissues on day 3, These results indicate the potential utility of local CD28-B7 costimulatory blockade for prevention of alloimmune and autoimmune destruction of pancreatic grafts in type 1 diabetic hosts.
