Fractalkine and macrophage-derived chemokine: T cell-attracting chemokinesexpressed in T cell area dendritic cells

Dendritic cells (DC) are a system of antigen-presenting cells specialized i n interaction with T cells. Recently it has been reported that DC can produ ce CC (beta) chemokines that attract T cells. In this study we isolated mou se fractalkine and macrophage-derived chemokine (MDC) belonging to CX3C (de lta) and CC chemokine families, respectively, from bone marrow-derived matu re DC. While expression of fractalkine, which has so Car been only examined in the brain and in vitro endothelial cells so far, was rather ubiquitous, MDC, which has been reported to be synthesized by macrophages and DC, was expressed specifically in the thymus and lymph node. This is the first repo rt that indicates fractalkine expression by DC. Expression of fractalkine a nd MDC mRNA increased with maturation of DG during in vitro culture of bone marrow cells. Spleen- and epidermis-derived mature DC in culture also expr essed these chemokines. Furthermore, their expression was detected selectiv ely by Northern hybridization in CD11c(+) B220(-) DC freshly purified from lymph nodes, and in large stellate cells in the lymph node T cell areas by in situ hybridization. Conditioned media of 293T cells transfected with the se chemokine cDNA were chemotactic to Con A-activated splenic T cells as we ll as the mouse T cell line EL4. In conclusion, while fractalkine and MDC b elong to different families of chemokines, both may be involved in recruitm ent of T cells for interaction with mature DC in the immune response.