MDC (macrophage-derived chemokine) is a 69-amino acid CC chemokine with a N-terminal sequence of 24 residues as a signal sequence. It was originally cloned from human monocyte-derived macrophages. Recombinant MDC attracts monocyte-derived dendritic cells, activated lymphocytes and natural killer cells. MDC has anti-HIV-1 activity. Expression of MDC mRNA in macrophages is enhanced by LPS, IL-1β and TNFα. MDC is a functional ligand for CCR4.