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11 Cards in this Set
- Front
- Back
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Why are inhibitors often activated at the same time as the enzyme in inflammation?
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You want to be able to shut down the inflammatory response rapidly. It's dangerous!
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How does the contact activation system work? What does kinogen turning into bradykinin cause? What mediates this reaction, and what does this have to do with Hageman factor?
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Vascular injury activates factor XII (Hageman factor). This activates Kallikrein, which mediates kinogen turning into bradykinin. Bradykinin causes vasodilation, edema, and pain. Kallikrein is activated by Hageman factor, but kallikrein itself also activates Hageman factor, causing a positive feedback
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Is coagulation and complement intertwined?
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Yes
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What are the three pathways leading to complement activation?
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Classical pathway (antigen:antibody complexes), the lectin pathway (lectin binding to pathogen surfaces), and the alternative pathway (pathogen surfaces)
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What are the three main functions of complement? What complement proteins mediate these mechanisms?
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- Inflammation: C3a, and C5a are anaphylatoxins. Anaphylatoxins simulate histamine - they cause vasodilation and increase vascular permeability. C5a is a chemotactic agent for neutrophils, monocytes.
- Phagocytosis - C3b opsonizes microbes and promotes phagocytosis - Cell lysis - Formation of the MAC complex lyses microbes. |
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How does the classical pathway work?
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Antibodies bind to antigen. The C1 complex (consisting of 1 C1q, 2 C1r, 2 C1s) binds to these antibodies. Binding activates C1r and C1s via cross proteolysis. C1s cleaves C4 into C4a and C4b. C4b binds to the surface of microbes. C2 binds to C4b, and is cut by C1s to create the C4bC2a complex, or C3 convertase
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What does C4bC2a, or C3 convertase do?
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It cleaves C3 into C3a and C3b. C3a is an anaphylatoxin. C3b binds to the complex to form C4bC2aC3b, or C3,5 convertase. C3,5 convertase cleaves C5 into C5a and C5b. C5a is an anaphylatoxin and a chemoattractant. C5b goes on to form the MAC complex
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Describe the formation of the MAC complex
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C5b binds to C6 and C7. The C5b67 complex binds to the membrane. C8 binds to this complex and inserts into the membrane. C9 binds to this complex and polymerizes, forming the MAC, which is a pore in the membrane
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How does complement assist in phagocytosis.
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Many C3b molecules bind to the bacterial surface (opsonization). However, C3b binding is not sufficient to engulf the bacteria - C5a must also bind in order for phagocytosis to occur
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Learn the alternative pathway
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Do it!
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Describe the classical pathway
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Antibodies bind to bacterial antigens. The C1 complement complex (1 C1Q, 2 C1R, and 2C1S) bind to the antibody
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