1What is complement? Where does it come from?
-proteins (C1-C9) secreted by liver and circulates in the blood
-they initiate a enzymatic pathway/cascade (complement proteins cleave and activate one another)
2What are the components of cleaved complement? be specific about function:
-a portion and b portion (independent functions)
-a portion causes mast cells to release histamine (result in inflammation)
-b portion coats microbes resulting in opsonization (enhanced phagocytosis of microbes)
3What are the three complement pathways of activation?
-Alternative pathway
-Lectin pathway
-Classical pathway
4Describe the alternative complement pathway?
-triggered when C3b portion binds to foreign cell surfaces (some C3b always present)
5Describe the lectin complement pathway?
-pattern recognition molecules bind to mannose portion of microbe cell wall and interacts with complement system components
6Describe the classical pathway?
-activated by antibodies that are bound to microbial invaders
7All three complement pathways lead to formation of
C3 convertase
8What does C3 convertase do in classical pathway? be specific
it is cleaved into C3a (leads to opsonization and cytolysis) and C3b (leads to inflammation)
9How is the alternative pathway triggered?
*C3b binding to microbial invaders
10How is the lectin pathway triggered?
*Mannose binding lectin (MBL) to microbial invaders
11How is the classical pathway triggered?
*antibodies binding to microbial invaders
12What does C3b activate?
-binds to microbe resulting in opsonization (enhanced phagocytosis of macrophage)
OR
-splits C5 into two components and uses C5b to create membrane attack complex to induce cytolysis of microbe
13What does C3a activate?
-activates mast cells to release histamine (increases blood vessel permeability and chemotactic attraction of phagocytes)
14What is required for classical complement system activation?
-need C1 bridge with two antibodies
15How is the alternative pathway complement system activated?
-complemet proteins (factor B, D, P) attatch to surface of pathogen then C3 binds!
16How is the lectin complement pathway activated?
-macrophage ingests microbes and release cytokines
-the liver is stimulateed to release lectins which bind to carbohydrates on bacteria surface
17What three ways do microbes use to evade complement evasions?
-capsules (prevent complement activation)
-surface lipid-carbohydrates (prevents membrane attack by MAC complex formation)
-producing enzymes to digest C5a (prevents histamin release)
18How is the complement system regulated?
-molecules in host cell membrane bind regulatory proteins and inactivate C3b (responsible for opsonization and inflammation)