Tolerogenic dendritic cells (DCs) represent a promising approach to promote transplantation tolerance. In this study, the potential of autologous bone marrow (BM)-derived murine DC to protect rat-to-mouse islets xenografts was analyzed.
Tolerogenic DCs were generated by differentiating BM cells in the presence of granulocyte-macrophage colony-stimulating factor and interleukin 10 (IL-10, IL-10 DC). The phenotype of IL-10 DC was characterized in vitro by expression of costimulatory/inhibitory molecules (flow cytometry) and cytokines (Luminex and ELISA), their function by phagocytosis and T-cell stimulation assays. To study transplant tolerance in vivo, rat islets were transplanted alone or in combination with autologous murine IL-10 DC under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. Xenograft survival was evaluated by monitoring glycemia, cellular infiltration of xenografts by microscopy and flow cytometry 10 days post-transplantation.
Compared with control DC, IL-10 DC exhibited lower levels of major histocompatibility complex class II, costimulatory molecules (CD40, CD86, CD205), lower production of pro-inflammatory cytokines (IL-12p70, TNF, IL-6), and higher production of IL-10. Phagocytosis of xenogeneic rat splenocytes was not impaired in IL-10 DC, whereas stimulation of T-cell proliferation was reduced in the presence of IL-10 DC. Xenograft survival of rat islets in diabetic mice co-transplanted with autologous murine IL-10 DC was significantly prolonged from 12 to 21 days, without additional immunosuppressive treatment. Overall, infiltration of xenografts by T cells and myeloid cells was not different in IL-10 DC recipient mice, but enriched for CD8 ⁺ T cells and myeloid cells with suppressor-associated phenotype.
Autologous IL-10-differentiated DC with tolerogenic properties prolong rat-to-mouse islets xenograft survival, potentially by locally inducing immune regulatory cells, indicating their potential for regulatory immune cell therapy in xenotransplantation.