The chemokine CC ligand 18 (CCL18), also known as pulmonary and activation-regulated chemokine (PARC), is produced primarily by antigen-presenting cells in the innate immune system, including dendritic cells, monocytes, and macrophages.CCL18 is involved in the attraction of naïve T cells, regulatory T cells, Th2 cells, immunosuppressive and immature dendritic cells, basophils, and naïve and effector B cells. Aberrant expression of CCL18 is observed in many diseases, including breast cancer, autoimmune diseases, and allergy, and it is thought that aberrant CCL18 expression plays a role in these disease processes.