The expression of receptors of chemokines, such as C-C chemokine receptor type 5 (CCR5) and CXC chemokine receptor 3 (CXCR3), on antigen-specific Treg support a role for proper trafficking of Treg to target tissue in the prevention of acute GVHD in murine models [11,12]. The gene discussed is CCR5; the disease is acute graft versus host disease.