CD11b+ cells in donor-specific transfusion prolonged allogenic skin graft survival through indoleamine 2,3-dioxygenase

• IDO induces tolerance through regulatory T cells in donor-specific transfusion.
• CD11b+ cell infusion resulted in prolongation of graft survival.
• Foxp3+CD4+CD25+ T cells increased in recipients infused with CD11b+ cells.
• High IDO expression was observed in CD11b+ cell infusion group.

The aim of this study is to show the effect of donor-specific transfusion (DST) in inducing immunological tolerance mediated by regulatory T cells (Treg) and indoleamine 2,3-dioxygenase (IDO). Skin grafts from H2d Balb/c were transplanted into H2k C3H/He 7 days after the infusion of donor splenocytes, isolated each immune cell populations. Graft survival prolonged in recipients who received splenocytes, MHC class II+ CD90− cells and CD3−CD19− cells (p < 0.001, p < 0.05 and p < 0.01, respectively). CD11b+ cell infusion resulted in prolongation of graft survival when compared to CD11c+ cell infusion (p < 0.01). Foxp3+CD4+CD25+ T cells were increased after the transplant in recipients infused with CD11b+ cells (p < 0.05). The mixed lymphocyte reaction showed donor-specificity (p < 0.001). High IDO expression was observed in CD11b+ cell infusion group. Graft survival with DST using IDO antagonist (1MT) were not prolonged. In conclusion, DST allows induction of donor-specific tolerance which involves Foxp3+CD4+CD25+ T cells and IDO expression.