MIP-3 beta/CCL19

CCL19, also known as MIP-3 beta, is an immunostable chemokine that is located on chromosome 9 in the human genome. CCL19 is abundantly expressed in the thymus and lymph nodes, moderately expressed in the trachea and colon, and less expressed in the stomach, small intestine, lung, kidney, and spleen. CCL19 binds to and functions as a chemokine receptor, CCR7. CCR7 is the first CCR7 is the first lymphocyte-specific G protein-coupled receptor (GPCR) identified with seven transmembrane alpha helices. CCR7 is expressed on both double-negative and single-positive thymocytes, including naive T cells, central memory T cells, regulatory T cells, naive B cells, semimature/mature DCs and NK cells, as well as a few tumor cells, where it serves as a key regulator for directing steady-state lymphocytes to secondary lymphoid organs. In contrast, CCL19 is the only chemokine known to effectively stimulate β-arrestin-mediated phosphorylation and internalization of CCR7, leading to receptor desensitization and migration of antigen (Ag)-presenting DCs, thereby affecting T cell responses. The CCL19-CCR7-based signaling pathway plays an important role in tissue immunity and inflammatory response memory. In addition, it also plays a role in vaccine-based protection against a variety of viruses, such as HIV-1 infection, hepatitis C virus (HCV), and herpes simplex virus 1 (HSV-1), etc. The interaction of CCL19 and CCR7 also contributes to the release of antiviral-associated cytokines (e.g., IFN-γ and IL-4) by immune cells, thereby promoting T cell proliferation and DC uptake of antigens^[1][2].