Chemotactic factor for t lymphocytes but not monocytes or granulocytes. May play a role in T-cell development in thymus and in trafficking and activation of mature T-cells. Binds to CCR4 and CCR8 (By similarity). Expressed in thymus and also in spleen, lung, lymph node, kidney, small intestine, colon and skin. Belongs to the intercrine beta (chemokine CC) family.