Complement pathway?
Answer:
The classical pathway of activation of the complement system is a group of blood proteins that mediate the specific antibody response. It is triggered by antigen-bound antibody molecules. It is the binding of a specific subdivision of the antibody molecule to the C1 component that initiates this pathway.
The alternative pathway of the complement system is a humoral component of the immune system's natural safety against infections which can operate without antibody association. The cascade begin with the spontaneous activation and attachment of the complement protein C3 to a pathogen, creating a catalytic activator that decay both spontaneously and quickly, but can head to the creation of a C3 convertase. The alternative pathway C3-convertase consists of the activated B and D factor, forming an unstable compound that can become stable after binding properdin, a serum protein. After the creation of C3 convertase, the complement system follows the same road regardless of the means of activation (alternative, classical, or MBL).
The most-recently discovered mannose-binding lectin pathway activate complement through the mannose-binding lectin protein. MBL binds to carbohydrates found on the surface of many pathogens. For example, MBL have been show to bind to yeasts such as Candida albicans , to virus such as HIV and influenza A, to many microbes including Salmonella and Streptococci , and to parasites similar to Leishmania.
http://www.nlm.nih.gov/cgi/mesh/2007/mb_...
http://www.biocarta.com/pathfiles/h_alte...
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