CCR5 and graft versus host disease: A recent study showed that tolerant patients without GVHD after HSC transplantation expressed significantly higher levels of CCR5 and CXCR3 compared with patients with acute GVHD early after HSC transplantation [8], suggesting that homing of Treg to secondary lymphoid tissues and sites of inflammation may play an important role in the control of GVHD.