Answer:
The complement system is a series of about 20 proteins that are involved in a cascade effect during an immune response. Complement is generally divided up into 3 pathways: classical, lectin, alternate. The classical pathway involves a complement protein binding to an antigen-antibody complex (and thus its role in adaptive immunity). Whereas in the alternate pathway, complement (C3) binds directly to the foreign cell( usaully bacteria). Thus its repsonse is non specific and therefore is also part of the innate imune system.