Blocking α4β7 binding to its constitutively expressed receptor MAdCAM-1 on intestinal endothelium with anti-MAdCAM-1 antibody after GVHD induction96, or using α4β7-deficient donor T cells95, selectively reduced CD8 T cell infiltration in the gut96 and led to less GI-GVHD95. The gene discussed is CD8A; the disease is graft versus host disease.