B Cell Activation and Memory

Question 1

3 main functions of antibodies

Answer 1

Neutralization of toxins
Opsonization of bacteria
Activation of complement

Question 2

Site of B cell activation

Answer 2

Secondary lymphoid organs (particularly the lymph nodes)

Question 3

First steps of B cell activation

Answer 3

1. B cells synapse with macrophages and dendritic cells to acquire antigen
2. B cells receive T cell help to become activated
3. Formation of germinal centers, IgM-bearing memory cells, and primary focus cells

Question 4

Germinal centers

Answer 4

Areas of proliferating B cells, which undergo somatic hypermutation, isotype switching, and differentiation into memory cells

Question 5

Primary focus cells

Answer 5

B cells that clonally expand and secrete IgM
Become plasma cells
Don’t undergo somatic hypermutation or isotype switching

Question 6

What causes lymph nodes to swell?

Answer 6

Rapid expansion of activated B cells

Question 7

Enzymes responsible for somatic hypermutation

Answer 7

Activation induced cytidine and adenine deaminases (AIDs)

Question 8

AID mechanism of action

Answer 8

Removal of amine group for cytosines and adenosines

Change amino acid sequence, resulting in different binding affinity of antibody

Question 9

Affinity maturation

Answer 9

B cells are selected because somatic hypermutation created better binding of their Ab pockets to antigen

Question 10

Isotype switching changes which antibody gene region?

Answer 10

Heavy chain constant region

Question 11

Difference between isotype switching and somatic hypermutation

Answer 11

Isotype switching changes constant region, not affecting antigen binding
Somatic hypermutation changes variable region, affecting antigen binding

Question 12

Memory B cell specifics

Answer 12

Live a long time
Circulate throughout the body
Replicate very quickly following subsequent antigen exposure