Trafficking of intra-graft T cells to recipients’ lymphoid organs after skin transplantation (TRAN3P.916)

Abstract

Abstract The skin contains T lymphocytes including significant numbers of FoxP3+ regulatory T cells (Tregs). However, their role in skin transplantation is still unknown. In this study, we investigated the trafficking of intra-graft donor T cells to the recipient’s lymphoid organs after skin transplantation in mice. To test this C57BL/6 (B6) mice received a skin transplant from a double transgenic B6 donor whose T cells expressed DSred while FoxP3 expression was associated with GFP (Tregs being double positive). At different time points after transplantation, cell suspensions of recipients’ lymph nodes, spleen and thymus were prepared. The presence and characterization of fluorescent donor cells was investigated using imaging flow cytometry analysis. First, the presence of T cells (DSred+ FoxP3-) was detected only at d4-d7 post-transplantation i.e. after skin graft revascularization and essentially in the host’s thymus. On the other hand, double positive (DSred+ FoxP3+) Tregs were found in all recipient’s lymphoid organs. Surprisingly, high frequencies of single positive GFP+ cells were found in both ipsilateral lymph nodes and thymus. The nature of these cells is being investigated. In summary, our results show that most T cells leaving the graft are Tregs spreading through all recipient’s lymphoid organs while other intra-graft T cells migrate preferentially to the host’s thymus.