Alternative Pathway of Complement Activation

The video tutorial by Kevin Tolkoff explains the complement activation pathways: classical, lectin, and alternative. The classical pathway requires antibodies, while the lectin pathway is antibody-independent, relying on mannose residues. The alternative pathway is unique, with baseline activity due to C3 hydrolysis. The video details the formation of the membrane attack complex, which disrupts pathogen membranes. The tutorial concludes with a preview of the next video, focusing on the functions of A fragments in the complement system.

What is required for the activation of the classical pathway?

• C3 hydrolysis

• Mannose residues

• Properdin

• Antibodies bound to antigens

Which pathway is antibody-independent and relies on sugars for activation?

• Classical pathway

• Lectin pathway

• Alternative pathway

• All of the above

What is the unique feature of the alternative pathway that allows it to have baseline activity?

• Mannose residues

• Presence of antibodies

• C3 hydrolysis in solution

• Properdin stabilization

What is the role of protein D in the alternative pathway?

• It splits protein B into BA and BB

• It forms the membrane attack complex

• It stabilizes the C3 convertase

• It binds to mannose residues

Which component remains bound in the complement system after protein splitting?

• D component

• A component

• B component

• C component

What is the function of the membrane attack complex (MAC)?

• To hydrolyze C3

• To form a pore in the pathogen membrane

• To bind antibodies

• To stabilize C3 convertase

Which protein stabilizes the C3 convertase in the alternative pathway?

• C5B

• Protein D

• Properdin

• C3B

What happens to the C5B component in the complement system?

• It binds to mannose residues

• It inserts into the membrane to start MAC formation

• It forms the C3 convertase

• It hydrolyzes C3

What is the fate of the A fragments in the complement system?

• They stabilize the C3 convertase

• They have important functions

• They bind to the pathogen surface

• They are discarded as waste

Which of the following is NOT a component of the membrane attack complex?

• C8

• C6

• C7

• C3