Complement cascade in the innate immune response
The classic pathway for the complement cascade involves the attachment of several initial complement proteins to an antibody-bound pathogen, followed by rapid activation and binding of many more complement proteins and the creation of destructive pores in the microbial cell envelope and cell wall. The alternate pathway does not involve antibody activation. Rather, C3 convertase spontaneously breaks down C3. Endogenous regulatory proteins prevent the complement complex from binding to host cells. Pathogens lacking these regulatory proteins are lysed.
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"OpenStax College, Innate Immune Response. October 17, 2013."
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