Allograft-specific cytokine profiles associate with clinical outcome after islet cell transplantation.

Islet cell transplantation can cure type 1 diabetes, but allograft rejection and recurrent autoimmunity may contribute to decreasing insulin independence over time. In this study we report the association of allograft-specific proliferative and cytokine profiles with clinical outcome. Peripheral blood mononuclear cells were obtained of 20 islet recipients. Cytokine values in mixed lymphocyte cultures (MLC) were determined using stimulator cells with graft-specific HLA class II. Qualitative and quantitative cytokine profiles were determined before and after islet transplantation, blinded from clinical outcome. Cytotoxic T Lymphocyte precursor (CTLp) assays were performed to determine HLA class I alloreactivity. Allograft-specific cytokine profiles were skewed toward a Th2 or regulatory (Treg) phenotype after transplantation in insulin-independent, but not in insulin-requiring recipients. IFNgamma/IL10 ratio and MLC proliferation decreased after transplantation in insulin-independent recipients (p = 0.006 and p = 0.01, respectively). Production of the Treg cytokine IL10 inversely correlated with proliferation in alloreactive MLC (p = 0.008) and CTLp (p = 0.005). Production of IL10 combined with low-MLC reactivity associated significantly with insulin independence. The significant correlation between allograft-specific cytokine profiles and clinical outcome may reflect the induction of immune regulation in successfully transplanted recipients. Islet donor-specific IL10 production correlates with low alloreactivity and superior islet function.

Human clonal CD8 autoreactivity to an IGRP islet epitope shared between mice and men.

Type 1 diabetes (T1D) is a multifactorial disease characterized by the infiltration and subsequent destruction of the pancreatic insulin-producing beta cells by autoreactive T cells. CD8(+) T cells play an essential role in this beta cell destruction. However, little is known about the target antigens of CD8(+) T cells in human T1D patients. The aim of this study was to assess whether an epitope derived from the islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP), IGRP(265-273,) which has recently been identified as a target in non-obese diabetic (NOD) mice and is fully homologous to the human epitope, is a target of human diabetogenic CD8(+) T cells. We isolated a human CD8 T cell clone against this epitope, which confirms that this IGRP epitope is shared across species.

Stable transplantation results of magnetically retracted islets: a novel method.

AIMS/HYPOTHESIS: Large quantities of pure viable donor islets are necessary for clinical transplantation. At present, low yields and low viability of pancreatic islets after transplantation necessitate the use of multiple donors for a single recipient. In this study an improved method for obtaining large quantities of pure viable islets of Langerhans for transplantation was developed in the rat. METHODS: Islets of Langerhans were isolated from Albino Oxford rats. The donor pancreata were perfused in situ with iron oxide, which resulted in entrapment of iron particles in the capillaries of the islets. Subsequently, the islets were isolated by magnetic retraction. Islets obtained with this method were compared with islets obtained by density gradient-isolated islets with respect to yields, purity, and insulin production capacity. Islets isolated with the magnetic retraction method were transplanted under the renal capsule of streptozotocin-induced diabetic recipients. Blood-glucose levels in the recipients were monitored for 2 months after transplantation. RESULTS: This method yielded more pure and viable islets than the conventional protocol. No contamination of exocrine tissue was observed after isolation. Furthermore, the islets isolated by magnetic retraction stained strongly positive for insulin during the entire observation period in vitro, and produced high amounts of insulin upon a challenge with glucose. The islets that were obtained by this new protocol were suitable for safe and effective transplantation. CONCLUSIONS/INTERPRETATION: We have shown that both the quantity and quality of islets obtained with this method were sufficient to induce insulin independence in a diabetic recipient using islets from only one donor.