Organ/tissue trafficking and distribution of Treg cells. Distinct chemokine receptors and integrin molecules implicated in Treg-cell organ/tissue trafficking and compartmentalization. Bone marrow–derived CXCL12 mediates Treg-cell bone marrow trafficking. Environmental CCL22 mediates Treg-cell trafficking into human ovarian cancer and mouse cardiac grafts. The lymphoid homing molecules CCR7 and CD62L may facilitate lymphoid homing of Treg cells. Certain CC chemokines and integrins may mediate Treg-cell trafficking into inflammatory tissues/organs.