MDC

MDC or CCL22, also named stimulated T cell chemotactic protein (STCP-1), is a CC chemokine initially isolated from clones of monocyte-derived macrophages. Human MDC cDNA encodes a precursor protein of 93 amino acid residues with a 24 amino acid residue predicted signal peptide that is cleaved to yield a 69 amino acid residue mature 8 kDa protein. At the amino acid sequence level, MDC shows less than 35% identity to other CC chemokine family members. Human MDC is expressed in dendritic cells, macrophages and activated monocytes. In addition, MDC expression is also detected in the tissues of thymus, lymph node and appendix. The gene for human MDC has been mapped to chromosome 16 rather than chromosome 17 where the genes for many human CC chemokines are clustered. Recombinant or chemically synthesized mature MDC has been shown to induce chemotaxis or Ca2+ mobilization in dendritic cells, IL2 activated NK cells, and activated T lymphocytes. A CD8+ T lymphocyte-derived secreted soluble activity that suppresses infection by primary non-syncytium-inducing and syncytium-inducing HIV1 isolates and the T cell line-adapted isolate HIV1 IIIB, has been identified as MDC. Based on aminoterminal sequence analysis, the major CD8 + T lymphocyte derived MDC protein yielded an aminoterminal sequence of YGANM, which is two amino acid residues shorter than the predicted mature MDC. The difference in potency between the two mature MDC isoforms has not been determined.