CCL17 also known as thymus and activation-related chemokine (TARC) is encoded by the CCL17 gene. It is expressed by thymus cells constitutively and phytohemagglutinin-stimulated peripheral blood mononuclear cells transiently. CCL17 signals through the chemokine receptors CCR4 and CCR8 and displays chemotactic activity for T lymphocytes and some other leukocytes. It plays an important role in skin diseases such as atopic dermatitis, bullous pemphigoid and mycosis fungoides. CCL17 has approximately 24 �?29 % amino acid sequence identity with RANTES, MIP-1α, MIP-1β, MCP-1, MCP-2, MCP-3 and I-309.