Regulating the expression of CD80/CD86 on dendritic cells to induce immune tolerance after xeno-islet transplantation

Abstract

Background: Antigen present cells (APCs) have been demonstrated to play dual roles in immune tolerance. Recently, compelling evidence indicates that APCs that express CD80, but not CD86 can protect allograft. We investigated whether modulation of CD80 in dendritic cells (DCs) offer protection for xeno-islets.

Methods: In vitro, isolated mature murine DCs received untransfection, transfection with CD86 siRNA or negative control siRNA. The DCs were used in mixed lymphocyte reaction in which rat islets and murine splenocytes were further added. On day 3 of co-culturing, the proliferation of lymphocytes was measured and interleukin (IL)-2, IL-4, IL-10, transforming growth factor β (TGF-β), interferon γ (INF-γ) and indoleamine 2,3-dioxygenase (IDO) from the supernatants were determined. Islets viability and function were also assessed. In vivo, streptozotocin-induced diabetic mice underwent rat islets transplantation were pre-treated with above DCs. At designated time, xeno-islets were subjected to histopathology, immunohistochemistry, survival time and functional tests. Peripheral blood T lymphocyte profiles were also examined.

Results: CD86-silenced-DCs had unchanged expression of CD80 and significantly suppressed the proliferation of lymphocytes. CD86-silenced-DCs simultaneously reduced IL-2 and INF-γ and increased IL-10, TGF-β and IDO, while had minimal effect on IL-4. The CD86-silenced-DCs also improved cell viability and function of xeno-islets when compared to untransfection and transfection control groups. In xeno-islets transplanted diabetic mice, transfer of CD86-silenced-DCs resulted in improved histopathology and dramatically prolonged survival time of the islets. These effects were also mirrored by the functional tests. Further analysis revealed that CD86-silenced-DCs had up-regulated levels of CD4(+)CD25(+)T cells in the peripheral blood compared to the other groups.

Conclusions: CD86-silenced-DCs induced immune tolerance of rat xeno-islets in recipient diabetic mice with up-regulated peripheral blood CD4(+)CD25(+)T cells.

Keywords: CD80/CD86; Dendritic cells; Diabetes; Immune tolerance; Pancreatic islet transplantation; Xenotransplantation.