Altered expression and endocytic function of CD205 in human dendritic cells, and detection of a CD205-DCL-1 fusion protein upon dendritic cell maturation

CD205 (DEC-205) is a member of the macrophage mannose receptor family of C-type lectins. These molecules are known to mediate a wide variety of biological functions including the capture and internalization of ligands for subsequent processing and presentation by dendritic cells. Although its ligands await identification, the endocytic properties of CD205 make it an ideal target for those wishing to design vaccines and targeted immunotherapies. We present a detailed analysis of CD205 expression, distribution and endocytosis in human monocyte-derived dendritic cells undergoing lipopolysaccharide-induced maturation. Unlike other members of the macrophage mannose receptor family, CD205 was up-regulated upon dendritic cell maturation. This increase was a result of de novo synthesis as well as a redistribution of molecules from endocytic compartments to the cell surface. Furthermore, the endocytic capacity of CD205 was abrogated and small amounts of the recently identified CD205-DCL-1 fusion protein were detected in mature DC. Our results suggest that CD205 has two distinct functions - one as an endocytic receptor on immature dendritic cells and a second as a non-endocytic molecule on mature dendritic cells - and further highlight its potential as an immuno-modulatory target for vaccine and immunotherapy development.