Pathogens appear to have evolved strategies to circumvent the capabilities of the complement system to eliminate them by dampening complement activation. Pathogens accomplish this evasion by affecting every facet of complement activation, including regulation of activation, amplification, opsonization, phagocytosis, chemoattraction, cell lysis (for a review, see Lambris et al. 2008; Rooijakkers and van Strijp 2007) by either proteolysis of complement proteins or mimicking the action of complement proteins or interacting with complement proteins. As will be seen below Staphylococcus aureus is a good example of a pathogen that subverts all these processes. Pathogens also take advantage of complement by binding to membrane bound complement proteins to gain entry into cells. For example, measles virus binds the membrane cofactor protein (MCP) and Epstein virus protein gp350/220 binds to CR2.