Question 15

Describe the components and function of the complement system including the role, activation and control?

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College Answer

Based on the question stem answers should have been structured to address the components of the complement system as well as the role, activation and regulatory mechanisms. A description of the components should include the number and type of molecule highlighting the important combinations of complement to produce the membrane attack complex. A description regarding the role in the innate immune response against bacterial infections was then required with a detailed description regarding the many ways this is achieved including opsonisation, phagocytosis, chemotaxis, mast cell/basophil activiation, lysis of cells and clearance of immune complexes. Information about the 3 pathways of activation where expected; classic, alternate and lectin pathyway, with some detail regarding the downstream effect of each that would take into account for the amplication of the response. The cessation of complement response is largely due to the limitatations of the half lives of the particular complement glycol-proteins or presence of specific inactivators.