complement regulation factors were some of the first transgenic pigs used for xenotransplantation. Complement control proteins also play a role in malignancy. Complement proteins protect against malignant cells- both by direct complement attack and through initiation of Complement-dependent cytotoxicity, which synergises with specific monoclonal antibody therapies. However, some malignant cells have been shown to have increased expression of membrane-bound complement control proteins, especially CD46, DAF and CD59. This mechanism allows some tumours to evade complement action. CCPs have been exploited extensively by pathogenic microbes. Neisseria gonorhoeae and Neisseria meningitidis, the bacteria responsible for gonorrhea and meningitis have many well-studied evasion strategies involving CCPs, including binding soluble regulators like Factor H and C4bp. Many viruses, such as Vaccinia incorporate mimics of CCPs into their envelope for the purposes of evading the complement system. Still other microbes such as the measles virus use CCPs as receptors to gain entry to cells during infection. Each of these strategies may provide targets for the development of vaccines, as with the case of N. meningitidis. Certain forms of schizophrenia are characterised by an underlying biological mechanism of excessive synaptic pruning, mediated by a dysregulated complement system in the brain. Accordingly, genetic variants of a brain-specific complement inhibitor, CSMD1, are associated with the risk of developing schizophrenia. Sources Further reading External links Complement system Proteins