The Classical Pathway

Question 1

The classical pathway involves

Answer 1

The interaction between antigen and antibody

Question 2

What’s the recognition unit of classical pathway

Answer 2

C1

Question 3

List the 3 subunits of C1

Answer 3

1. C1q
2. C1r
3. C1s

Question 4

Which subunit of C1 consists of a collagenous region with 6 globular head groups globe and serves as a recognition unit

Answer 4

C1q

Question 5

What happens when antibody binds to antigen

Answer 5

The binding site for the globular head group of C1q are exposed to Fc region of the antibody

Question 6

What is needed for for C1q to initiate the cascade

Answer 6

1. C1q must at least attach to 2 Fc fragments

2. Requires at least 2 molecules of IgG or 1 molecule of IgM

Question 7

C1q binding causes

Answer 7

C1r to enzymatically activate C1s

Question 8

C1s cleaves

Answer 8

1. C4 into C4a and C4b

2. CW into C2a and C2b

Question 9

C1 combines with C4b to form C1C4b. What’s the importance of C1C4b

Answer 9

It’s an enzyme which converts C2 into C2a and C2b

Question 10

C1C4b2a (C1C4b +C2a) forms an enzyme called

Answer 10

C3 convertase which converts C3 into C3a and C3b

Question 11

What is C3b

Answer 11

It’s an opsonin

Opsonin are molecules that bind to both bacteria and phagocytes

Question 12

What’s the importance of C3a

Answer 12

Increases the inflammatory response by binding to mast cells and causing them to release histamine

Question 13

What makes up the C3 activation complex

Answer 13

C4a and C2a

Question 14

When C3b binds to C4b and C2a, it forms a new complex called

Answer 14

C5 activation complex

Question 15

C5 activation complex C4bC2aC3b activates C5 proteins by cleaving them into

Answer 15

C5a and C5b

Question 16

Why is C5b considered the largest product

Answer 16

Because it combines with C6 -C9 to form C5b6789 (membrane attack complex)

Question 17

What C5 proteins has a low affinity for bacterial wall

Answer 17

C5b

Question 18

List the functions of C5b

Answer 18

1. Binds to mast cells and increases inflammation
2. Most powerful chemotactic factor known for leukocytes
3. It disperses away bacteria

Question 19

What molecular complex causes a change in membrane permeability

Answer 19

C5b6789 ( membrane attack unit)

Question 20

Define opsonization

Answer 20

Enhancement of phagocytosis by coating with C3b

Question 21

Define inflammation

Answer 21

Increase of blood vessel permeability and chemotactic attraction of phagocytes

Question 22

Describe cytolysis

Answer 22

Loss of cellular contents through transmembrane channel formed by membrane attack complex