ABSTRACT
In 1914 Gunn measured hemolytic complement activity in sera from patients with various bacterial infections and stated that "In all diseases, especially acute infectious diseases, it may be assumed as probable that, in the development of immunity". An extensive literature attests to the potential of complement as one of the primary defenses against a variety of microorganisms. Rough Gram-negative bacteria readily react with complement and are nonvirulent, whereas smooth organisms are less reactive and more virulent; unencapsulated staphylococci and pneumococci behave likewise. Complement activation occurs in a number of syndromes of sepsis: Gram-negative sepsis, pneumococcal pneumonia and bacteremia, cryptococcal sepsis, and dengue shock syndrome. Oldstone and Dixon have emphasized that complement-mediated lysis of virus-infected cells may be one mechanism of host injury during viral infections. Complement activation by generally nonpathogenic or mildly pathogenic Propionibacteria may mediate the inflammatory events of acne vulgaris.
