The soluble form of CD83 dramatically changes the cytoskeleton of dendritic cells.

CD83 is the best-known surface marker for mature dendritic cells (DC) and recently we could show that a soluble form of CD83 inhibits DC maturation. In addition, this soluble form inhibits DC-mediated T cell proliferation in vitro and in vivo. Furthermore, several viruses induce CD83 degradation or shedding in infected DC. A soluble form of CD83 was also found in plasma and serum of healthy individuals and interestingly at highly elevated levels in a number of haematological malignancies. Thus, CD83 also has functional implications for the immune response. However, the molecular mechanism is not well defined. Here we describe for the first time that soluble CD83 completely changed the cytoskeleton (analysed using phalloidin-, tubulin- and fascin-specific antibodies) when administered at a concentration of 10 microg/ml to mature DC. The cells rounded off and had only short, truncated, or no veils at all. Furthermore, soluble CD83-treated cells were completely inhibited in their ability to form clusters with T cells, an absolute prerequisite in order to stimulate T cells.