Innate immunity and hemostasis in aHUS. aHUS shows that regulatory proteins are vital for homeostasis. MCP and factor H protect cells from complement attack. Factor H can also transfer from plasma to cellular matrices such as an exposed basement membrane. Damage to an endothelial surface could result from a stressed, apoptotic, or necrotic cell that exposes the underlying basement membrane. The innate immune system responds to this injury state and facilitates wound repair. Excessive activation of the AP results in aHUS. (Used with permission from Tarr et al.²⁰ )