Human CCL20 (C-C motif chemokine ligand 20, also known as MIP-3α, macrophage inflammatory protein-3 alpha, or LARC – liver and activation-regulated chemokine) is a pro-inflammatory chemokine that plays a key role in mucosal immune defense and leukocyte trafficking. CCL20 signals specifically through the CCR6 receptor, promoting chemotaxis of immune cells including immature dendritic cells, memory T cells, Th17 cells, regulatory T cells, and certain B cell populations to sites of epithelial infection or inflammation. In humans, CCL20 is produced by epithelial cells, fibroblasts, endothelial cells, and immune cells in response to inflammatory stimuli such as microbial products, cytokines (e.g., IL-1β, TNF-α, and IL-17), and tissue injury. It is highly expressed at mucosal surfaces, including the intestinal tract, respiratory epithelium, skin, and reproductive tract, where it contributes to recruitment of antigen-presenting cells and initiation of adaptive immune responses. Dysregulated CCL20 expression is implicated in several chronic inflammatory and autoimmune diseases, including inflammatory bowel disease, psoriasis, rheumatoid arthritis, and multiple sclerosis, largely through its role in recruiting CCR6⁺ Th17 cells. CCL20 also contributes to tumor microenvironment modulation in certain cancers by influencing immune cell infiltration and inflammation. As a central mediator of mucosal immunity and Th17-associated inflammation, human CCL20 is widely studied as a biomarker of inflammatory activation and a potential therapeutic target in autoimmune disease, infection, and cancer.