Macrophage-derived chemokine (MDC, CCL22) is a member of the CC-chemokine family and is composed of 69 amino acid residues. MDC is mainly produced by macrophages and dendritic cells upon the stimulation with microbial products, or anti-CD40 antibody, and is upregulated by TH2-type cytokines, such as IL-4 and -5, but is downregulated by TH1-type cytokines, such as IFN-gamma. MDC-production is also upregulated by prostaglandin and cyclic AMP-elevating agents. MDC causes chemotactic migration of dendritic cells and TH2 cells. Furthermore, MDC is highly-expressed in the lesions of TH2-related diseases, such as airway hypersensitivity and atopic dermatitis. Thus, MDC plays an important role in the recruitment of TH2 cells into the inflammatory sites and the regulation of TH2-related immune responses.