MDC （CCL22） is a small cytokine that belongs to the CC chemokine family. CCL22 is one of several Cys-Cys （CC） cytokine genes clustered on the q arm of chromosome 16.
MDC shows chemotactic activity for natural killer cells， chronically activated T lymphocytes， monocytes and dendritic cells. On the other hand， MDC shows a mild activity for primary activated T lymphocytes and has no chemoattractant activity for neutrophils， eosinophils and resting T lymphocytes. MDC may also have a role in the trafficking of activated T lymphocytes to inflammatory sites and other aspects of activated T lymphocyte physiology. MDC interacts with cell surface chemokine receptors CCR4.
