Macrophage-Derived Chemokine (MDC/CCL22) and CCR4 Are Involved in the Formation of T Lymphocyte-Dendritic Cell Clusters in Human Inflamed Skin and Secondary Lymphoid Tissue

Our previous study demonstrated formation of T cell-dendritic cell (DC) clusters in inflamed dermis of intraorally autotransplanted skin flaps. Such T cell-DC clusters are supposed to be important for close interactions between T cells and DCs including the specific antigen presentation. Here we show the involvement of the macrophage-derived chemokine (MDC/CCL22) and its specific receptor CC chemokine receptor 4 (CCR4) in the formation of T cell-DC clusters. Reverse transcriptase-polymerase chain reaction analysis revealed high levels of mRNA expression for MDC and CCR4 in inflamed skin and neck lymph nodes (LNs), but not in normal skin. Immunohistochemically, MDC + cells and CCR4 + cells were mainly located within the T cell-DC clusters both in the dermis of inflamed skin and the T cell area of LNs. MDC + cells were identified to be DCs both in inflamed skin and LNs. The majority of CCR4 + cells were CD4 + T cells, accounting for approximately one-third of total CD4 + T cells in the inflamed skin. Our data suggest that the MDC-CCR4 system plays an important role in the formation of T cell-DC clusters both in inflamed skin and LNs.