Transplantation of insulin-producing tissue.

A series of new findings have shown that it is possible to prevent rejection of islet allografts and islet xenografts in animals without the continued use of immunosuppressive agents. The survival of allografts of rat islets has been prolonged for more than 100 days by in vitro culture of the islets at 24 degrees C for seven days prior to transplantation in conjunction with a single injection of rat antilymphocyte serum at the time of transplantation, Xenograft survival of rat islets transplanted into diabetic mice has been prolonged for more than 100 days by the use of culture of rat islets at low temperature, with a single injection of antiserums to mouse and rat lymphocytes at the time of transplantation. Rejection of established islet allografts in rats was induced by the injection of donor peritoneal exudate cells and donor T lymphocytes, whereas the injection of B lymphocytes did not induce rejection. The pretreatment regimens used for prolonging islet allograft and xenograft survival apparently destroy or alter passenger leukocytes in the grafts, and it would appear that these cells are needed for the induction of immune recognition by the recipient. Islet cells in mice express products of the H-2K and H-2D loci, but the cells do not express the I region (Ia) antigens. These new developments in the prevention of immune rejection of the islets raise the question as to whether these approaches may be applicable to the transplantation of islets into human subjects with diabetes.