Chemokine (C-C Motif) Ligand 1 (CCL1) is a small glycoprotein secreted by activated T cells, which play a central role during immunoregulatory and inflammaion processes. Human CCL1 has been assumed to be a homologue of the mouse TCA3. While the two proteins share only approximately 42% amino acid sequence identity, both chemokines contain an extra pair of cysteine residues not found in most other chemokines. CCL1 attracts monocytes, NK cells, and immature B cells and dendritic cells by interacting with cell surface chemokine receptor CCR8. CCL1 is identified as a potent inhibitor of HIV-1 envelope-mediated cell-cell fusion and virus infection.