Antigen-presenting cells can influence development of GVHD at multiple levels. Initial tissue injury and innate immune activation may trigger APC within tissues and induce certain APC populations such as DCs to migrate to draining lymph nodes. Migrating DCs or other lymph node resident APCs “trap” graft-versus-host-reactive T cells at this site for 3 to 4 days where they induce T cell activation and may “imprint” a homing phenotype that permits selective trafficking of effector cells to GVHD target organs. APCs within inflamed tissues may act to amplify the developing GVH response by providing further priming signals to T cells in situ by producing proinflammatory cytokines or actively recruiting T cells and other cellular effectors to this site.