TARC Human

Thymus and Activation Regulated Chemokine (TARC), also known as CCL17, is a chemokine that plays a crucial role in the immune system. It is produced by the thymus and various antigen-presenting cells, including dendritic cells, macrophages, and monocytes . CCL17 is involved in the chemotaxis of T-helper cells, particularly type 2 helper T cells (Th2), and is significant in various immune responses .

The CCL17 gene is located on chromosome 16 in humans . The protein encoded by this gene is a member of the CC chemokine family, characterized by two adjacent cysteines near their amino terminus . The structure of CCL17 allows it to bind to specific receptors on the surface of target cells, facilitating its role in immune cell signaling and migration .

CCL17 functions primarily by binding to the CCR4 receptor, which is expressed on Th2 cells, regulatory T cells, and other immune cells . This binding induces chemotaxis, guiding these cells to sites of inflammation or immune response . CCL17 is constitutively produced in the thymus and can be upregulated in response to certain stimuli, such as phytohemagglutinin-stimulated peripheral blood mononuclear cells .

CCL17 has been implicated in various diseases, particularly those involving immune dysregulation. It plays a complex role in cancer, where it can attract T-regulatory cells, allowing some cancers to evade the immune response . Conversely, in other cancers like melanoma, increased levels of CCL17 are associated with improved outcomes . Additionally, CCL17 is linked to autoimmune and allergic diseases, where it contributes to the recruitment of immune cells to affected tissues .

The clinical relevance of CCL17 extends to its potential as a diagnostic and therapeutic target. Elevated levels of CCL17 can indicate certain eosinophilic disorders and other immune-related conditions . Understanding the regulation and function of CCL17 can aid in developing treatments for diseases characterized by immune cell infiltration and inflammation .