Chemotactic activity for lymphocytes but not for monocytes or neutrophils. In thymus, mediates medullary accumulation of thymic dendritic cells and contributes to regulatoy T cell development, playing a role in self-tolerance establishment. Expressed in activated CD8(+) T cells. In the thymus, expressed by medullary thymic epithelial cells. The thymus of knockout mice shows a lower medullary accumulation of dendritic cells. Animals have a defective generation of naturally ocurring regulatory T cells. Belongs to the intercrine gamma family.