CCL27, also known as CTACK, is a small cytokine belonging to the CC chemokine family. Members of this family are proteins characterized by two adjacent cysteines. CCL27 is chemotactic for skin-associated memory T lymphocytes. CCL27 may also play a role in mediating homing of lymphocytes to cutaneous sites. CCL27 plays a pivotal role in establishing the inflammatory infiltrate characteristic for common inflammatory skin diseases. Through binding to the chemokine receptor 1 (CCR1), CCL27 mediates inflammation by promoting lymphocyte migration into the skin.

Human Chemokine (C-C Motif) Ligand 27 (CCL27) is a small cytokine that is a member of the CC chemokine family; it is expressed in numerous tissues, including gonads, thymus, placenta and skin. CCL27 elicits its chemotactic effects by binding to the chemokine receptor CCR10. Predominantly expressed in the skin, CCL27 is associated with T cell-mediated inflammation of the skin. Human and Mouse CCL27 share 84% sequence identity in the mature form.

CCL11 or chemokine (C-C motif) ligand 11 is a member of the chemokine (C-C motif) ligand family. Chemokin (C-C motif) ligand 11 is a member of the chemokine family. There are four members of the chemokine family: C-C kemokines, C kemokines, CXC kemokines and CX3C kemokines. The C-C kemokines have two cysteines nearby the amino terminus. There have been at least 27 distinct members of this subgroup reported for mammals, called C-C chemokine ligands (CCL)-1 to 28. Chemokines are a family of small chemotactic cytokines, or proteins secreted by cells. They share the same structure similarities such as small size, and the presence of four cysteine residues in conserved locations in order to form their 3-dimensional shape. Some of the chemokines are considered pro-inflammatory which can be induced to recruit cells of the immune system to a site of infection during an immune response, while others are considered homeostatic and are implied in controlling the migration of cells during normal processes of tissue maintenance and development. CCL11 is implicated in allergic responses through selectively recruiting eosinophils by inducing their chemotaxis. The effects of CCL11 are mediated by its binding to chemokine receptor. Increased CCL11 levels in blood plasma are associated with aging in mice.