Dendritic cells (DC) not only initiate T cell responses, but are also involved in the induction of tolerance. The functional properties of DC are strictly dependent on their state of maturation. It has been shown that immature DC can induce immune tolerance and prolong allograft survival. Interleukin-10 (IL-10) is an important immunosuppressive cytokine which inhibits maturation and function of DC. In order to improve the tolerogenicity of DC, we and others showed that adenovirus vectors can effectively mediate IL-10 genetic modification of DC, and IL-10 genetic modification can inhibit MHC II, B7.2, and CD40 expression, IL-12 secretion and the T cell stimulatory capacity of DC. The primary aim of this study is to examine the in vivo effects of this approach on allograft survival in a murine cardiac allograft transplantation model. To our surprise,we observed that infusion of immature DC genetically modified to express IL-10 (DC-IL-10) via the tail vein could not prolong allograft survival in the recipients, but shortened their survival. More interestingly, portal venous infusion of DC-IL-10 markedly prolonged allograft survival. The diverse effects of DC-IL-10 infusion through different routes may be due to the different immune responses to alloantigens in recipients that received DC-IL-10 via either the portal or the tail vein. Decreased cytotoxicity, polarization of Th2 response, poor T cell stimulating activity of liver DC and enhanced incidence of donor DC in the recipients may contribute to the more efficient prolongation of allograft survival observed after portal venous infusion of DC-IL-10. These results suggest that portal venous infusion may be an effective approach for immature DC to induce immune tolerance or hyporesponsiveness against donor antigens, and prolong allograft survival.
Copyright 2004 Springer-Verlag