Dendritic Cell-based Tolerance Induction in a Murine Model of Corneal Allograft Rejection

Abstract

Abstract: : Purpose: Dendritic cells (DCs) are known inducers of immunity but more recently have been recognised as mediators of immunological tolerance. Our aim was to evaluate the role of syngeneic immature DC-based tolerance induction in a murine model of corneal allograft rejection. Methods: DCs were enriched from bone marrow cultures in the presence granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor beta 2 (TGFbeta-2). PBS or 10⁶ TGFbeta-treated DC were injected subcutaneously into the nape of the neck (s.c.) of syngeneic recipient mice and corneal allografts were performed seven days after s.c. injection. Three days post corneal transplantation, cervical lymph nodes were separately dissected as submandibular (SM) and superficial cervical (SC) lymph node (LN). Draining LN cells were tested for proliferation in an MLR and cytokine production by ELISA. The phenotype of drainging LN cells was examined by flow cytometry (FCM). The eyes were evaluated by clinical observation at various times. Results: Administration of TGFbeta-treated DC by s.c. injection induced strong proliferation and cytokine production only in SC LN cells. Low levels of IFN-γ and high levels of IL-10 were present in MLR supernatant from cultured SC LN after DC s.c. injection. FCM analysis indicated there was a downregulation of CD3⁺CD4⁺CD44⁺ T cells and an upregulation of CD4⁺CD25⁺CTLA-4⁺ T regulatory cells (Treg) in the SC LN following TGFbeta-treated DC s.c. administration. Compared to controls, TGFbeta-DC treatment prolonged the mean corneal graft survival time significantly (16.75±3.4d vs 26±4.05d, P<0.01). Conclusions: This study has shown immature syngeneic DCs have the potential to prolong corneal allograft survival as DC are directed towards the SC LN, a site previously known to be involved in mucosal tolerance. Upregulation of Treg and the high amounts of Th2 cytokines in SC LN may have contributed to this protective effect.

Keywords: immune tolerance/privilege • cornea: basic science • injection