CCL17

CCL17, also known as thymic and activating regulatory chemokine (TARC), is a powerful chemokine commonly associated with type 2 immune responses, and its encoding gene is located on chromosome 16 in humans. CCL17 can be produced by thymic and antigen-presenting cells such as dendritic cells, macrophages, and monocytes, and acts by binding to the cell surface chemokine receptor CCR4. CCR4 is a G protein-coupled receptor expressed as a chemokine receptor on Th2 cells, cutaneous lymphocytes skin-localized T cells and regulatory T cells, and also on T cells in adult T-cell leukemia/lymphoma and cutaneous T-cell lymphoma. CCR4 has an important role in the regulation of immune homeostasis and activation of innate immune cells in the central nervous system (CNS). CCL17 plays an important role in the recruitment of CCR4-positive Th2 lymphocytes, is involved in the transport of Th2 cells in eosinophil-associated diseases (including AA and AD) and may be involved in the transport of tumor cells in certain T-cell lymphomas.CCL17 is also thought to be a homeostatic and inducible neuromodulatory chemokine that maintains the typical highly branching morphology of hippocampal microglia under homeostatic conditions and promotes adaptation of microglia morphology to acute LPS-induced neuroinflammation. CCL17 is also associated with autoimmune and allergic disorders^[1][2].