The complement system, as part of the innate immunity, has important functions, such as cell opsonization during phagocytosis (through complement components C1q-, C3b-, and iC3b), immune cell recruitment, inflammation induction (through the release of C3a and C5a) and during the formation of the Membrane Attack Complex (MAC) leading to pathogens lysis during infections. The gene discussed is C3; the disease is infection.