This gene is one of several Cys-Cys (CC) cytokine genes clustered on the q arm of chromosome 17. Cytokines are a family of secreted proteins involved in immunoregulatory and inflammatory processes. The CC cytokines are proteins characterized by two adjacent cysteines.

Chemokine (C-C motif) ligand 18 (CCL18) is a small cytokine belonging to the CC chemokine family that was previously called PARC (pulmonary and activation-regulated chemokine). CCL18 is approximately 60% identical in amino acid sequence to CCL3. It is expressed at high levels in lung and at lower levels in certain lymphoid tissues, such as the lymph nodes, and is chemotactic for activated T cells and nonactivated lymphocytes.The gene for human CCL18 contains three exons and is located on chromosome 17.