ISLET-SPLENOCYTE CO-TRANSPLANTATION ABOLISHES AUTOIMMUNE-DRIVEN PRIMARY NON-FUNCTION IN THE NON-OBESE DIABETIC MOUSE

Abstract

158 Clinical islet transplantation remains relatively unsuccessful in comparison to whole pancreas transplantation. Evidence from the BB rat model of spontaneous diabetes demonstrates that isolated islets transplants are peculiarly sensitive to recurrent autoimmunity but co-transplantation of pancreatic lymph node cells from diabetes resistant donors leads to engraftment of a donor T cell population (RT6+) that prevents recurrent autoimmune destruction of islet isografts and allografts. This model is limited by the severe T lymphopenia of the BB rat. Demonstration of this finding in a non-lymphopenic model, the non-obese diabetic (NOD) mouse, would significantly increase the likelihood that this finding is clinically applicable. METHODS: 500 islets from 4-6 week old NOD mouse donors were transplanted under the renal capsule of autoimmune diabetic (NOD-Au) or streptozocin (300 mg/kg) diabetic (NOD-Sz) mice. Some cohorts simultaneously received ˜75 million H-2 matched non-obese resistant (NOR) splenocytes (SPL) by tail vein and/or recipient pre-treatment with the CD4 depleting mab GK1.5 400 µg/kg on days -7,-2,-1 and 0. FACS analysis confirmed CD4 depletion to < 1%. Graft failure was determined by blood glucose >200 mg/dl on two consecutive days. Immunoblot analysis assessed mouse RT6 expression in prediabetic and diabetic NOD and NOD islet/SPL recipients. RESULTS: Table Immunoblot analysis revealed that splenocyte RT6 expression was identical in naive prediabetic NOD, NOR and NOD recipients of successful islet transplants but not autoimmune diabetic NOD animals. CONCLUSIONS: These results demonstrate that primary nonfunction of islet transplants in autoimmune diabetic NOD recipients is autoimmune-driven since islet transplants in chemically diabetic NOD mice function indefinitely. CD4 depletion and NOR splenocyte co-transplantation restores RT6 expression to pre-diabetic levels leading to ablation of the autoimmune-driven primary non-function of islet transplants. This data confirms that in a non-lymphopenic animal model recurrent autoimmunity can be avoided with addition of donor immune cells at the time of transplantation.Table