The role of exocrine tissue in pancreatic islet transplantation.

Isolated pancreatic islet transplantation has been proposed as a possible way of treating diabetes, but despite extensive experimental research, successful clinical transplantation remains elusive. A major problem has been the isolation of sufficient viable islet tissue for transplantation, especially from the human pancreas. It is possible to improve the yield of islet tissue by omitting purification steps, and unpurified dispersed pancreas has been successfully transplanted experimentally. However, attempts to apply the same technique clinically have been unsuccessful and have produced unacceptable complications. There is evidence that exocrine contamination may impair the implantation of islet tissue when transplanted to restricted sites, such as the kidney capsule. Yet, complete purification of islet tissue is probably not necessary for safe transplantation with adequate implantation of tissue in sites such as the spleen or liver. Exocrine tissue may be more immunogenic than islet tissue, and complete purification may have advantages for the prevention of rejection.