What does CCR4 primarily bind to in the context of T-cell migration?

CCR4 is a chemokine receptor that plays a crucial role in T-cell migration and homeostasis. In the context of T-cell migration, CCR4 primarily binds to the chemokines CCL17 (also known as thymus and activation-regulated chemokine, or TARC) and CCL22 (also referred to as macrophage-derived chemokine, or MDC). This binding is essential for guiding T cells, particularly regulatory T cells (Tregs) and Th2 cells, to sites of inflammation or specific tissues.

Both CCL17 and CCL22 are involved in immune response regulation and attract CCR4-expressing T cells. This interaction facilitates the accumulation of these T cells in areas where they are needed, contributing to the immune response. Therefore, the binding of CCR4 to both CCL17 and CCL22 is critical in mediating Th2-type immune responses and maintaining immune homeostasis.

Understanding the function of CCR4 and its ligands is essential in immunology, as it provides insights into T-cell behavior in various pathologies, including allergies, asthma, and cancer.