C7, one of the components of the terminal complement complex (TCC), also know as the membrane attack complex (MAC). Proteolytic cleavage of C5 by C5 convertase generates C5b which initiates assembly of the C5b-9 MAC. This complex is assembled from five precursor molecules in the serum, finalized with the polymerization of C9 which accompanies insertion of the complex into the cell membrane causing cellular lysis. C7 occupies an important position in the TCC cascade. C7 undergoes a hydrophilic-amphiphilic transition following activation. It enables the developing MAC to bind directly to target cell membranes. C7 has been shown to exhibit genetic polymorphism. Polymorphonuclear leukocytes represent a major source of C7. The fact that inflammatory cells have the potential to secrete C7 suggests an important role for locally produced complement in the inflammatory process.