Human CCL15 (C-C motif chemokine ligand 15), also known as leukotactin-1 (Lkn-1) or MIP-1δ, is a member of the CC chemokine family involved in leukocyte recruitment and inflammatory regulation. CCL15 is produced primarily by epithelial cells, hepatocytes, monocytes, macrophages, and certain tumor cells in response to inflammatory cytokines and immune stimulation. It is synthesized as a precursor protein that undergoes proteolytic processing to generate more active forms with enhanced chemotactic potency. CCL15 signals mainly through the CCR1 receptor to promote chemotaxis and activation of monocytes, neutrophils, eosinophils, and specific T lymphocyte subsets. In healthy individuals, circulating CCL15 levels are generally low but detectable; expression increases during inflammatory conditions, infection, and certain malignancies. Elevated CCL15 has been associated with chronic inflammatory diseases, atherosclerosis, liver disease, and tumor progression, where it may contribute to recruitment of myeloid cells into the tumor microenvironment. In clinical and translational research, human CCL15 serves as a biomarker of inflammatory activation and immune cell trafficking and is being investigated as a potential therapeutic target in inflammatory disorders and cancer.