Block 3 Complement TOKA

Question 1

What is the key site for activation of the complement system?

Answer 1

On the surface of pathogens

Question 2

What are the 3 pathways of the complement system?

Answer 2

Classical, Lectin, and Alternative

Question 3

What are the end results of complement activation?

Answer 3

Recruit other cells

Opsonize pathogens

Kill pathogens (MAC)

Question 4

What effector components do all 3 complement pathways generate?

Answer 4

C3 which turns into C3a and C3b

Question 5

How does the 1st pathway work to recruit inflammatory cells?

Answer 5

Some complements act as CHEMOATTRACTANTS to recruit phagocytic cells to sites of complement activation (chemotaxis)

Question 6

What is the second way of protection in the complement system?

Answer 6

complement proteins bind to pathogens and opsonize them for phagocytosis

Question 7

What is the 3rd way of protection in the complement system?

Answer 7

Killing of pathogens by creating pores in the membrane

osmotic burst (MAC)

Question 8

How does the complement system work to activate the adaptive immune system?

Answer 8

1. Opsonization by complements alerts APCs to target microbes
2. B cells with complement receptors allow them to enhance response to microbes

Question 9

Which one has the enzymatic activity? C3a or C3b

Answer 9

C3a

this is an exception, usually the b is the one w enzymatic activity

Question 10

How are complement components of the alternative pathway designated?

Answer 10

by Factors

Ex: Factor B

Bb is the one w enzymatic activity

Question 11

How is the classical pathway inititated?

Answer 11

By binding of C1q

Question 12

C1q functions?

Answer 12

The first protein in the classical pathway cascade

C1q binds to the surface of a pathogen by

1. binding directing to bacteria (Lipoteichoic acid)
2. Binding to C reactive proteins that bind to phosphocholine on bacteria
3. Binding to antigen-antibody complex (MOST EFFECTIVE)

Question 13

How is the lectin pathway initiated?

Answer 13

By binding of carbohydrate-binding proteins to carbs on pathogens

Question 14

What are the carbohydrate-binding proteins involved in the lectin pathway?

Answer 14

1. Mannose binding lectin (MBL) (binds to mannose containing carbs on microbes)
2. Ficolins (binds NAG on surface of microbes)

Question 15

How is the alternative pathway initiated?

Answer 15

By binding of spontaneously derived C3b to pathogen

Question 16

All 3 pathways lead to generation of?

Answer 16

C3 convertase

Question 17

C3 convertase functions?

Answer 17

binds to pathogen

cleaves C3 to C3b and C3a

Question 18

C3b

Answer 18

the MAIN effector molecule of the complement system

produced by C3 convertase cleaving C3 to yield C3b

acts as a OPSONIN to target pathogen for destruction

can also bind to C3 convertase to yield C5 convertase which converts C5 to C5a and C5b

Question 19

C3a

Answer 19

a mediator of inflammation

produced by C3 convertase which cleaves C3 to yield C3a and C3b

Question 20

How is C5b produced?

Answer 20

C3b binds to C3 convertase to make C5 convertase

C5 convertase then cleaves C5 to C5a and C5b

Question 21

C5b

Answer 21

initiates the last event in complement activation

made by C3b binding to C3 convertase to make C5 convertase which cleaves C5 to C5a and C5b

Question 22

What are potent activators of the classical complement pathway?

Answer 22

IgM and IgG

they bind to the antigen and allow the Fc region to be open

C1qrs binds to the Fc region

Question 23

C1q

Answer 23

binds to the Fc region on IgM and IgG on the pathogen of the classical pathway

C1q has 6 globular heads

tails of C1q have C1r and C1s

Question 24

How is C1 activated?

Answer 24

when 2 heads of C1q bind to the Fc regions of antibodies bound to the antigen

Question 25

C4b

Answer 25

attaches to the surface of the microbe or to the Ag-Ab complex

Question 26

C1s

Answer 26

cleaves C2 into C2b and C2a

C2a has the enzymatic activity (exception)