Biology 380 Spring 2010 Immunology Henson Lec. 4: Innate Immunity III 1. Complement is a proteolytic cascade of serum proteins that “complement” the actions of antibodies. A. Early experiments showed: - heat (56 degrees C) labile nature. - not related to anti-toxins/antibodies.- multiple components that acted sequentially. B. Three major pathways: - Classical activated by antibodies or CRP. - Lectin activated by mannose-binding lectin protein.- Alternate activated by microbial surfaces. C. Effector functions:- Anaphylatoxins (C3a, C4a, C5a) mediate inflammation, extravasation, and chemotaxis.- C3b performs opsonization leading to phagocytosis, solubilization and immune complex clearance.2. Toll-like receptors. A. Different types are specific for different pathogens and can be extracellular or intracellular. B. Signaling pathways tend to be of two types:- Activation of kinase cascade ⇒ IRF3 ⇒ produce interferons = anti-viral.
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