Background: Type 1 diabetes is a cell-mediated autoimmune disease. Successful transplantation of human fetal pancreatic tissue into type 1 diabetic patients must address both autoimmunity and allograft rejection. We investigated whether humoral and cellular responses to islet antigens could be demonstrated in the peripheral blood of type 1 diabetic subjects receiving human fetal pancreatic tissue transplants.
Methods: We investigated peripheral blood mononuclear cell (PBMC) responses, using cellular immunoblotting, and autoantibody responses to islet proteins, before transplant and at 3-month intervals after transplant, of nine long-term type 1 diabetes patients (mean disease duration of 21 years) receiving human fetal pancreatic tissue subcutaneously into the abdominal wall without immunosuppression.
Results: Before transplant, all nine subjects were islet cell autoantibody (ICA)-negative and seven out of nine subjects were glutamic acid decarboxylase autoantibody (GADAb)-positive. After transplant, all subjects became ICA(+) and the two patients who were GADAb(-) before transplant became GADAb(+) after transplant. Maximum PBMC reactivity to separated human fetal pancreatic proteins was observed in four patients 3 months after transplant, in one patient at 6 months, in two patients at 9 months, and in one patient at 12 months after transplant. One subject, who had PBMC reactivity to multiple islet proteins before transplant, continued to respond to multiple islet proteins throughout the study.
Conclusions: We conclude that the development in the peripheral blood of ICA, GADAb, and PBMC reactivity to human fetal pancreatic proteins in the trans plant recipients is most consistent with reactivation of the type 1 diabetes disease process.