Complement 1

Question 1

What is complement?

Answer 1

The heat-labile anti-microbial component in blood

Question 2

Does each antibody have its own complement protein?

Answer 2

No

Question 3

Role of complement?

Answer 3

Enhances/complements the ability of antibodies and phagocytic cells

Question 4

How many plasma proteins are involved in the complement system?

Answer 4

~20

Question 5

Which system can the complement system work with?

Answer 5

The clotting system

Question 6

What are the three pillars of the complement system?

Answer 6

Release of small bioactive fragments
Fragments of the complement proteins bind to activating agents
Destroy the invader organism by forming pores on the target cell

Question 7

Which small, bioactive fragments does complement release?

Answer 7

Small protein fragments–> anaphylatoxins

Question 8

Role of anaphylatoxins?

Answer 8

Cause inflammation when cleaved
Can recruit cells to go to the site of infection if they are cleaved near to a microbe

Question 9

What is opsonization?

Answer 9

Fragments of complement proteins binding to the activating agents

Question 10

What do fragments of complement proteins cause to be formed once bound to a microbial cell surface?

Answer 10

Membrane attack complex

Question 11

What are the three complement pathways?

Answer 11

Alternative pathway, lectin pathway, classical pathway

Question 12

Why is the alternative pathway not exactly a pathway?

Answer 12

It is more of an acceleration mechanism–> once complement is activated it makes sure it stays activated

Question 13

Lectin pathway?

Answer 13

Complement binds to sugars on surfaces

Question 14

Oldest pathway of the complement system?

Answer 14

Lectin pathway

Question 15

Which complement pathway evolved last?

Answer 15

Classical pathway

Question 16

What is the classical pathway?

Answer 16

C-reactive protein/antibody binds to specific antigen on the pathogen surface

Question 17

What do all three complement pathways lead to?

Answer 17

Cleavage of C3

Question 18

What is the central complement component?

Answer 18

C3

Question 19

What is c3 cleaved into?

Answer 19

c3a and c3b

Question 20

What is C3A?

Answer 20

An anaphylatoxin

Question 21

What is C3B?

Answer 21

An opsonin that binds covalently onto the surface of the microb/dead cells and tags the for destruction by phagocytes

Question 22

Which part of c3 is important for the recruitment of immune cells?

Answer 22

C3A

Question 23

Which complement components are involved in the classical pathway?

Answer 23

C1, C2, C4

Question 24

Which complement components are involved in the lectin pathway?

Answer 24

MBL, MASP, C2, C4

Question 25

Which complement components are involved in the alternative pathway?

Answer 25

C3, B, D

Question 26

What do the different components of the complement system all end up forming?

Answer 26

C3 convertase enzyme

Question 27

What does C3 convertase enzyme do?

Answer 27

Converts C3 into C3A and C3B

Question 28

Why do anaphylatoxin fragments have an a after them (e.g. C4a)?

Answer 28

They are acidic

Question 29

Why do opsonin (surface binding) fragments have an a after them (e.g. C5b)?

Answer 29

They are basic

Question 30

What is C4a, C3a, C5a involved in?

Answer 30

Phagocyte recruitment

Question 31

What is the most active anaphylatoxin?

Answer 31

C5a

Question 32

How can complement cause damage?

Answer 32

Virus e.g. covid sits in lungs and activates it continuously--> inflammation Also occurs in stroke--> complement overactivated which does a lot of damage