Vitronectin Antibody (Polyclonal)

In contrast to membrane-formed C5b-9 complexes, C5b-9 complexes formed in the fluid phase contain an additional protein, the S protein. Subsequently, it was found that isolated S protein inhibited C5b-9 attachment. S protein functions like a “membrane analogue” in that it binds to the binding site generated on assembly of C5b-9 and is required for insertion of the complex into the membrane. As a result, SC5b-7, SC5b-8 or SC5b-9 complexes are formed which have lost their membrane-binding capacity. When the S protein was cloned and sequenced, it was found to be identical to Vitronectin. Within the complement cascade, Vitronectin not only inhibits attachment of C5b-9 to target cells, but also prevents C9 polymerization. The biological function of Vitronectin is to minimize complement-mediated attack of cells near an ongoing complement attack.