Complement and diseases: defective alternative pathway control results in kidney and eye diseases.

The complement system is a central part of innate immunity and in its normal setting aimed to recognize and eliminate microbes. For elimination toxic activation products are generated locally and are reported directly of the surface of the invading microbe. A deregulation of the alternative pathway results in defective recognition and toxic activation products can be formed on the surface of host tissues and structures. Recent studies have shown that mutated or defective regulators of the alternative pathway of complement are associated with auto immune diseases of the kidney, including the atypical form of hemolytic uremic syndrome (HUS), membranoproliferative glomerulonephritis (MPGN) and also of the eye, such as age-related macular degeneration (ARMD). Current research provides clues how mutations occurring in genes coding for single complement components or the inactivation of single regulators lead to defective alternative pathway amplification, via the convertase C3bBb. These scenarios explain how defects of a single regulator lead to local, organ specific damage.