IMMUNOGLOBULINS
CLASSICAL ALTERNATE AND LECTIN PATHWAYS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Cleaves C3b and C4b
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Acts as a cofactor with I to inactivate C4b
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Cofactor with I to inactivate C3b
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Dissociates C2b or Bb from binding sites
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Detailed explanation-1: -Factor I (C3b inactivator, C3bINA) cleaves C4b and C3b into products that are recognized by specific cellular receptors, as discussed below. The sequential cleavage of C3b by factor I to iC3b and C3dg is depicted in Figure 20.4. C4b is cleaved in an analogous manner to C4d.
Detailed explanation-2: -Factor I (FI) is a crucial inhibitor controlling all complement pathways due to its ability to degrade activated complement proteins C3b and C4b in the presence of cofactors such as factor H, C4b-binding protein, complement receptor 1 or CD46.
Detailed explanation-3: -C4b Binding Protein Acts as an Innate Immune Effector Against Influenza A Virus. C4b Binding Protein (C4BP) is a major fluid phase inhibitor of the classical and lectin pathways of the complement system. Complement inhibition is achieved by binding to and restricting the role of activated complement component C4b.