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74 Cards in this Set
- Front
- Back
Classical pathway [LO]
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[LO]
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Lectin pathway [LO]
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[LO]
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alternate complement pathway [LO]
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[LO]
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Role of constituent proteins [LO]
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[LO]
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role of the complement system in protecting from and causing disease. [LO]
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[LO]
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what is the role of the C3ac5a split product?
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Aggregation of platelets.
Chemotactic for leukocytes (C5a >>>> C3a). Acts on mast cells --> histamine --> vasodilation --> ↑↑ vascular permeability. |
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What is the role of the split product C3a & C5a
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Are rapidly degraded by serum carboxypeptidase
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What is the role of the split product C3b
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Opsonisation (process whereby opsonins make an invading microorganism more susceptible to phagocytosis).
Bystander lysis. |
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What is the role of the split product C5b
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Opsonisation (process whereby opsonins make an invading microorganism more susceptible to phagocytosis).
Bystander lysis. |
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What is the role of the split product C1 INH
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Removes C1r and C1s from C1q
Binds to C1rC1s blocking activity |
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What is the role of the split product Factor 1
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Cleaves C3b, C4b into inactive forms
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What is the role of the split product Factor H
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Inhibits C3bB formation
Disrupts C3bBb complexes Acts with Factor I – ↑ decay of C3b --> C3c + C3d |
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What is the role of the regulatory protein CR1
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Binds C4b, displacing C2b.
Binds C3b, displacing Bb. Cofactor for Factor I (FI; which regulates complement activation by cleaving cell-bound or fluid phase C3b and C4b. |
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What is the role of the regulatory protein DAF
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Same function as CR1 except it doesn’t at as a cofactor for Factor I.
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What is the role of the regulatory protein MCP
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Increases inactivation of C3b and C4b.
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What is the role of the regulatory protein Vitronectin (S protein)
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Prevents C5b, C6 and C7 binding to membrane.
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What is the role of the regulatory protein CD59?
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Prevents C5b – C7 formation on homologous cells
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What is the role of the regulatory protein (Thermal instability)?
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Very short half life (T1/2).
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What are the AgAb complexes in the Classical pathway?
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C1q, C1r, C1s, C4, C2
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What are the mannose binding lectin or ficolin binds carbohydrates on pathogen surfaces?
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MBL, MASP-2, C4, C2
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What are the proteins on the pathogen surfaces of the alternative pathway?
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C3, B factor, D factor
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What does C3a do?
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peptide mediator of:
1. inflammation 2. phagocyte recruitment |
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What is the function of C3b
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1. Binds to complement receptors of phagocytes
2. Opsonisation of pathogens 3. Removal of immune complexes |
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What are the Terminal Complement components?
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C5b, C6, C7, C8, C9
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Where does C1q bind?
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Multiple Fc regions
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Which Abs does C1q bind?
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IgM, IgG1, IgG3
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Where does complement reside?
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It is confined to the surface on which it is initiated.
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Describe what C1-INH does
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Describe the actions of the C1 inhibitor
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What removes C1r and C1s
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What can remove MASPs?
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What does the Factor I do?
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What does Factor I have to be bound to be a regulator?
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CR1 or the Membrane cofactor protein
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What breaks c3b down to ic3b and C3dg?
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Factor I
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What does FI do to both C3b and C4b?
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C3b --> ic3b and c3dg
C4b --> c4c, c4d |
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What are the serine protease inhibitors in the complement system
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C1-INH and Factor I
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What displaces Bb in the alternate complement pathway?
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Factor H
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What is C4BP?
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cofactor for factor I, cleaves c4b to C4d, C4c
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function of DAF
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Competes with B for C3b
Splits up C4b2a and c3bBb with CR1 And prevents MAC with CD59 |
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Where does DAf reside? What does it to in conjunction with what?
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on host cells also dissociate C4b2a and C3bBb in conjunction with CR1
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What prohibits the MaC from forming?
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CD59 and DAF on host cells prevent binding of C9 in MAC complex
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What does CD59 do?
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What are the classical pathway deficiencies?
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C1 deficiency
C2 deficiency C4 definciency |
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What are the symptoms and prognostics of C1 deficiency?
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skin and kidney disorders- pts rarely reach adulthood
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What is the most common classical pathway deficiency?
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C2 deficiency, has milder effects
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What is C4 deficiency
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coded in 2 genes
partial deficiency more common |
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What are deficiencies associated with alternate and lectin pathways?
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What happens if deficient in C1-INH
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desregulated bradykinin production (Bradykinin is a peptide that causes blood vessels to dilate (enlarge))
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What causes dysreagulation of bradykinin
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C1-INH deficiency
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What causes C1-INH deficiency
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autosomal dominant hereditary angioedema
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What is the good news about hereditary angioedema?
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transient - however life threatening if airways blocked
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How is hereditary angioedema treated?
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C1-INH concentrate doses
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What occurs if a factor H mutation exists
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Impaired C3 convertase -->
atypical haemolytic uraemic sydrome endothelial damage --> fibrin depostion Haemolytic anaemia thrombocytopenia renal failure |
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Which deficiency causes the following and why?
atypical haemolytic uraemic sydrome endothelial damage --> fibrin depostion Haemolytic anaemia thrombocytopenia renal failure |
Impaired C3 convertase by factor H deficiency - Factor H inhibits Bb and therefore cannot convert to c3a, c3b (positive feedback)
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What deficiency causes PNH and complement mediated red cell lysis
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CD59 and DAF
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What does CD59 and DAF deficiencies cause
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CD59 - prevent membrane complexes
DAF - usurps Bb for binding with c3b, membrane complexes and prevents c5 convertase when with - splits c3bBb, c4b2a Causes paroxymal nocturnal haemoglobinuria and complement mediated red cell lysis |
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When is classical pathway used?
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Ag Ab complexes
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When is lectin pathway used?
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microbes with terminal manose groups or acetylated sugars
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When is alternative pathway used?
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bacteria, fungi virus or tumour cells.
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What deficiencies cause lupus like disease?
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C1, C2, C4
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What deficiencies cause severe recurrent bacterial infections?
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C3
fH fI B D |
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What deficiencies cause neisserial infection?
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Factor P
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What causes RECURRENT Neisserial infection?
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c6, c7, c8, c9
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What is complement testing performed on?
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fresh serum
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Describe classical pathway screen
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Describe Alternative pathway screen
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Describe Opsonisation
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Describe the agents responsible for chemotaxis and inflammation
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C3a and C5a:
‘anaphylatoxins’ |
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What is the c3aR located on?
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esinophils, basophils more than neutrophils
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Where is the c5aR found?
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white cells
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What does the binding of c3aR or c5aR do?
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++ adhesive properties of host cells
+++ extravasion primes phagocytes to excrete enzymes, vasoactive amines and inflammatory cytokines • swelling, heat and pain • fever and shock • C3a and C5a: ‘anaphylatoxins’ |
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What does C3b perform?
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from classical pathway coats and opsonises the aggregated complex
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What is the role of CR1 and where is it located?
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CR1 on red cells binds C3b (and C4b) to carry the complex to sites of macrophage residency
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What primes B cells?
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Binding of antigen bound to C3 fragments enhances antigen specific B cell selection and maturation
Ag bound to BCR, C3 fragment (C3d) bound to CR2 |