Graft-infiltrating cells expressing a CD200 transgene prolong allogeneic skin graft survival in association with local increases in Foxp3+Treg and mast cells

► Graft infiltrating CD200+ cells suppress MLCs in vitro in antigen-specific fashion. ► Grafts in CD200tg mice are associated with infiltrating Foxp3+Treg and mast cells. ► Mast cells in graft infiltrate in CD200tg mice are not suppressive in vitro. ► Suppression of mast cell degranulation by CD200+ cells increases graft survival.