The high expression of CX3CR1 on the surface of CD8+T cells and the overexpression of its ligand CX3CL1 in the intestinal mucosa of patients with acute GVHD suggest the critical role of the CX3CR1/CX3CL1 axis in intestinal infiltration and damage during acute GVHD (100). The gene discussed is CD8A; the disease is acute graft versus host disease.