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12 Cards in this Set
- Front
- Back
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Define antibody mediated cell cytotoxicity. What 2 cells utilize ADCC? What isotypes are involved?
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Process by which Fc receptors on a cell bind Fc portion of antigen bound antibodies resulting in activation of that cell. NK cells via IgG lyse target cells and eosinophils via IgE kill helminths.
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An overwhelming proportion of a single clone of IgM antibodies in serum is suggestive of what disease?
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Waldenstrom's macroglobinemia. Because IgM is the largest Ig with the most binding sites, patients with advanced disease are likely to exhibit hyperviscosity syndrome, which can lead to irreversible blindness.
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An overwhelming proportion of a single clone of IgG or IgA antibodies in serum is suggestive of what disease?
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Multiple myeloma. Patients afflicted by this disease often exhibit punched out lytic lesions within the bones, resulting in bone pain and hypercalcemia.
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Name the three complemented pathways and how they are activated.
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The classical complement pathway is activated when IgM or IgG bind a microbial surface(cell wall) followed by binding of C1 enzyme to the Fc antibody fragments.
Thealternative pathway is activated directly when C3b binds first a microbial cell surface and then binds factor B. |
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How is the Lectin pathway activated?
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By mannose binding lectin(MBL), which recognizes terminal mannose residues on microbial cell surfaces. MBL then triggers other proteases.
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Why do free IgM or IgG not activate the complement cascade?
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Binding of IgM/IgG to a microbial surface exposes the complement binding regions.
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How do IgM and IgG differ with respect to binding C1?
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Only one IgM molecule is needed, whereas atleast two IgG molecules are needed to bind C1. Thus IgM is more potent at activating complement.
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C3 convertase cleaves C3 to C3a(and C3b) in each complement pathway, but how does C3 convertase differ among pathways?
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Classical and lectin pathways; C3 convertase is(C4b, 2a).
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In the alternative pathway: C3 convertase is (3b, Bb). TRUE/FALSE
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TRUE.
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In the classical and lectin pathways what enzymes cleave C4 to C4b(and C4a) and C2 to C2a(and C2b)?
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Classical: C1 (subunits C1q binds the Fc fragment, C1r and C1s are proteolytic)
Lectin: Proteases triggered by MBL. |
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In the alternative pathway a small amount of C3 can cleave itself(for opsonization). Once C3b binds B( forming C3b, B) on a microbial surface, what enzyme cleaves B?
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Factor D cleaves B to Bb, converting C3b, B to C3b, Bb(C3 convertase).
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C5 convertase cleaves C5 C5 to C5a(and C5b) in each complement pathway, but how does C5 convertase differ among pathways?
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Classical and lectin: C5 convertase is C4b, 2a 3b
Alternative: C5 convertase is C3b, Bb C3b Therefore, C5 convertase is C3 convertase + 3b. |
