Complement System Pathways and Functions

The video explains the complement system, a series of proteins in the blood that play a crucial role in immune responses. It covers the classical and alternative pathways, detailing how proteins like C1 to C9 interact to destroy pathogens. The classical pathway involves an antigen-antibody complex, while the alternative pathway directly binds to pathogens. Both pathways recruit phagocytes, tag pathogens for destruction, and form a membrane attack complex to eliminate threats. The video concludes with a preview of the next topic on T-cells and adaptive immunity.

What is the primary role of the complement system in the body?

• To digest food

• To regulate blood pressure

• To assist in immune responses

• To transport oxygen

Where are complement proteins primarily produced?

• In the liver

• In the kidneys

• In the lungs

• In the heart

What triggers the classical pathway of the complement system?

• High blood pressure

• Presence of water

• Antigen-antibody complex

• Direct binding to pathogens

Which complement protein is the first to bind in the classical pathway?

• C3

• C5

• C1

• C9

What is the function of the C3a fragment in the complement system?

• To split C5

• To form the membrane attack complex

• To bind to pathogens

• To attract phagocytes

What is the final outcome of the membrane attack complex formation?

• Pathogen replication

• Pathogen destruction

• Pathogen mutation

• Pathogen dormancy

How does the alternative pathway differ from the classical pathway?

• It does not involve complement proteins

• It begins with direct binding of C3 to the pathogen

• It requires an antigen-antibody complex

• It starts with C1

Which proteins interact with C3 in the alternative pathway?

• Factor P, B, and D

• Factor L, M, and N

• Factor X, Y, and Z

• Factor A, B, and C

What is a key feature of the classical pathway?

• It involves direct pathogen binding

• It is non-specific

• It is part of the specific immune response

• It does not involve antibodies

What is the main similarity between the classical and alternative pathways?

• Both form the membrane attack complex

• Both start with C1

• Both are non-specific

• Both skip C3