Lecture 5 - Complement

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What role do C3a and C5a play in inflammation?

Suppress the opsonization of pathogens

Inhibit the release of proinflammatory cytokines

Recruit phagocytes and promote inflammation (correct)

Prevent anaphylactic shock

How do complement receptors connect complement-tagged pathogens to effector cells?

Through inhibition of proinflammatory cytokine release

By stimulating the release of granule components from phagocytes

By facilitating the binding of complement-tagged pathogens to effector cells (correct)

By promoting pathogen lysis

How does opsonization enhance phagocytosis?

Prevents pathogen lysis

Makes pathogens more readily taken up by phagocytosis (correct)

Reduces the uptake of pathogens by phagocytes

Promotes inflammation

What is the function of properdin (factor P) in the alternative pathway of complement activation?

Stabilizes C3 convertase (C3bBb) Signup and view all the answers

Which complement factor creates the membrane-attack complex (MAC) that leads to pathogen lysis?

Multiple complement factors Signup and view all the answers

What is the main downstream effect of large amounts of C3a and C5a?

Anaphylactic shock Signup and view all the answers

What is the key mechanism of action of the complement system related to inflammation?

Increasing vascular permeability and chemotaxis Signup and view all the answers

Which process involves the coating of a pathogen's surface to make it more easily ingested by phagocytes?

Opsonization Signup and view all the answers

What is the main function of phagocytosis in cellular processes?

Facilitating engulfment of pathogens Signup and view all the answers

How is the complement system initially activated?

Via three pathways: Classical, Alternative, Lectin Signup and view all the answers

Which proteins circulate in the blood until activated and initiate their respective complement reactions?

Pro-proteases Signup and view all the answers

Which fragment of the complement system identified by 'a' after its name has a specific function?

'a' fragment Signup and view all the answers

What is the main function of C3 convertase in the complement system?

Cleave C3 into C3a and C3b Signup and view all the answers

What is the role of negative regulation in complement activation?

Preventing excessive activation and damage to host tissues Signup and view all the answers

Which pathway is triggered by soluble proteins known as lectins?

Lectin pathway itself Signup and view all the answers

What is the role of pro-proteases in the complement system?

Initiate complement reactions by cleaving and activating the next protein in the sequence Signup and view all the answers

What is one of the main outcomes of inhibiting the formation of MAC on host cells?

Protection of host cells from damage Signup and view all the answers

Which protein prevents the appearance of C3 convertase under normal/basal conditions?

CD59 (Protectin) Signup and view all the answers

Which molecule is involved in enhancing inflammation according to the text?

C3a Signup and view all the answers

What is the main function of C3b as discussed in the text?

Opsonization Signup and view all the answers

Which protein is involved in the negative regulation of MAC formation by inhibiting the assembly of the Membrane Attack Complex?

CD59 (Protectin) Signup and view all the answers

Which pathway results in the generation of C3 convertase (C4b2a) according to the text?

Classical pathway Signup and view all the answers

What is the function of C3b in the complement system?

Pathogen lysis Signup and view all the answers

What initiates an amplification loop for C3b formation in the alternative pathway?

Factor B and protease factor D Signup and view all the answers

Which outcome is NOT associated with complement activation?

Pathogen growth promotion Signup and view all the answers

Which molecule is involved in phagocytosis enhancement in the complement system?

C3b Signup and view all the answers

What happens under normal/basal conditions due to the presence of complement-regulatory proteins?

Prevention of complement activation progression Signup and view all the answers

What is the role of C1q in the complement system based on the text?

Directly binding pathogens Signup and view all the answers