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37 Cards in this Set
- Front
- Back
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Complement is the major effector of the ______ ______ of the immune system
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Humoral Branch
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Activation of complement
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Stimulates a closely regulated cascade of enzymes to facilitate Ag clearance and generate inflamatory response
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2 goals of complement
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Facilitate Ag clearance and generate a quick inflammatory response
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Three pathways of complement system
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classical, alternative, and lectin
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Complement components are synthesized in what 3 locations?
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liver, macrophages, and epithelial cells of the gastric and genitourinary tracts
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Complement makes up _____% of the serum globulin factor
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15%
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Proenzyme
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innactive form that when activated can start complement
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Each component of complement has a long/short half life. Explain why this is.
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They have a short half life so they only act locally and cant travel too far to do damage
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Explain the naming system for complement
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They each get the letter C followed by a number and sometimes a lower case letter. The lower that letter is in the alphabet the smaller it is. Example: C3a is smalled than C3b.
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If a fragment or combinatin has _____ activity it gets a line above it
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enzymatic
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MAC stands for...
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Membrane Attack Complex
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Three pathways to MAC are...
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classical, alternative, and lectin
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Classical pathway is initiated by what 2 things
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1. formation of soluble Ag:Ab complexes
2. Binding of Ab to Ag on a suitable traget like bacterial cell |
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C1q has how many heads and does what
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It has 6 heads that interact with Ab. Must bind at least 2 of the heads to activate complement
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IgM can activate which pathway
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classical
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Pentameric IgM gives how many binding sites for C1q?
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3 binding sites
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Monomeric IgG has how many binding sites and how does this effect the number you need to start complement
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Only can bind 1 C1q so you need at least 2 to start complement
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Alternative pathway is activated by what
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It is activated by cell surface constituents foreign to the host. Cell wall components of Gram + and Gram - bacteria especially
**Does not require Ab for activation |
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Lectin Pathway is activated by what
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Activated by binding of the pattern recognition receptor MBL
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MBL
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Mannose binding lection
An acute phase protein that is produced in an inflammatory response. Important innate defense mechanism |
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What does MAC do
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Forms a transmembrane channel that disrupts the membrane and allows leakage of small molecules and ions resulting in death
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When MAC's go bad they...
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Can attack bystander cells which do not deserve killing and this is the basis for autoimmune diseases
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The complement system is non-specific/specific
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It is non-specific bc it can attack normal host cells as well as microorganisms. **Needs to be closely regulated
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Component lability
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Very short half lives which doesnt allow them to travel far- 40 nm
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Inactivating regulatory proteins
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Block the function of complement
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Complement-binding receptors
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Each circulating RBC and WBC has receptors for complement
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Complement receptors do 2 things
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1. Mediate many biological activities of the complement system
2. regulate the complement system by binding active complement components and degrading them |
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Cell lysis is done by which 2 pathways
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alternative and lectin
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How are cells lysed in complement?
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Similar to method of enveloped virus where envelope is derived from membrane
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Gram - cells are most susceptible to MAC. When can they not be?
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Gram negative (-) unless they have built up LPS in cell wall
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Gram positive cells are susceptible as well. When can they not be?
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If they have built up enough peptiodglycan in their cell walls.
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Nucleated cells are harder lyse because...
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Unlike RBC's that only require one MAC, nucleated cells require many to lyse a cell
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Infammatory response is initiated by cleavage products that...
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Bind to receptors on mast cells and basophils and induce degranulation and histamine release
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anaphylatoxins
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split products that cause degranulation
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Main opsonin of complements system is...
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C3b
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How does C3b work?
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It coats immune complex and binds to RBC's which is carried to the liver where it is killed
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Complement deficiencies
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C3 deficiencies are the most severe
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