Chapter 7 Complement

Question 1

Complement: Describe how they circulate around the immune system, how they need to be activated and how it interacts with the innate and adaptive immunity

Answer 1

inactively, activate each other through cascade

Innate= induces phagocytosis
Adaptive= binds to antibodies

Question 2

What are the 4 main functions of complement?

Answer 2

• Lysis via MAC
• inflammation by C4a and C5&C3a (anaphalylatoxins)
• opsonization by C3b
• immunoclearance: removal of immunocomplexes by phagocytosis, carried to spleen and liver

Question 3

What is complement made of, how much of serum does it make up? Which subunits are larger with what exception?

Answer 3

made of soluble and glyco-proteins, synthesized in liver. Make up 5% of serum. b sub unit larger except for C2

Question 4

What are the 3 pathways for complement activation? What are the ways each is initiated? Give the 3 ways the alternative pathway can be activated.

Answer 4

Classical: Abs/Ag, cleaves C1

Lectin: Sugar PAMPs, Lectins bind to microbial surfaces,
lectins serve as MBL-associated serine proteases

(MASP’s)–> cleaves C4 and C2 to form C3 convertase.
alternative: iniated by alternative ticker, alternative properdin and alternative protease., initiated by cell surface components that are foreign to host (LPS and teichoic acid)

Question 5

Draw out the entire complement cascade.

Answer 5

sd

Question 6

How does complement become regulated?

• 3 ways
• Why is regulation crucial
• Why is C3 convertase a major step?

Answer 6

• CD59 (protectin)–> inhibits polymerization of C9
• C1 inhibitor of classical pathway
• undergo spontaneous inactivation if not stabalized

Crucial because it does damage to surrounding tissue, must be inactive if not needed.
C3 convertase is a major amplification step in ALL pathways= has short half life, controlled by regulatory proteins, most clinical problems occur here.

Question 7

How do gram (+) and gram (-) evade or resist MAC complex?

Answer 7

gram + = thick peptidoglycan

gram - = long poly sac chains, prevent penetration of MAC

Question 8

Revise 4 more ways complement aids the immune system.

Answer 8

• inflammation via C3a and C5a anaphylatoxins induce smooth muscle contraction and increases vascular permeability.
• opsonization by C3b and C4b
• viral neutralization
• clearance of immunocomplexes: coated by C3b and carried to liver.

Question 9

What is systemic lupus erthmatosus? (SLE)

Answer 9

Complement deficiency, loss of immunoclearing.