Maturation-dependent expression of C1q-binding proteins on the cell surface of human monocyte-derived dendritic cells

The expression and cell surface levels of many important receptors are dependent on the maturation stage of dendritic cells (DCs), and related to the unique function of immature and mature DCs. In this report, we show for the first time that human monocyte-derived DCs express two types of Clq-receptors, gClqR and cClqR. Furthermore, immature DCs secrete detectable amount of Clq into the culture supernatant. Immature DCs express higher cell surface levels of both ClqRs than mature ones, while the total ClqR protein and mRNA levels remain the same. The following experimental evidence supports this conclusion. (1) Inflammatory cytokines and LPS, which induce maturation of DCs, downregulate surface expression of both ClqR molecules. (2) Cytokines and drugs (IL-10, IFNalpha, dexamethasone) that keep I)Cs phenotypically and functionally immature significantly upregulate the cell surface expression of both ClqRs. (3) Neither of these treatments changed the intracellular gClqR level nor the gCl qR mRNA levels measured by real-time RT-PCR. The elevated surface expression of ClqRs on DCs has been found not to be due to increased apoptosis or cell death as the result of DC treatment. Taken together, these data show that human monocyte-derived DCs express gClqR and cCl qR, their expression on the cell surface is maturation dependent and imature DCs secrete Clq. These data strongly suggest the role of ClqRs in immature DC function and in the regulation of immune processes. (C) 2003 Published by Elsevier Science B.V.