B-Cell Mediated Immunity

Question 1

Cross-linking of surface IgM on antigen is known as _____

Answer 1

Clustering

Question 2

Explain the cascade of events that occur immediately after clustering to trigger changes in gene expression.

Answer 2

1. Activation of tyrosine kinase
2. Igα and Igβ phosphorylated at ITAMs Blk, Fyn, or Lyn
3. Syk binds Igβ tail
4. Changes in gene expression

Question 3

What are the functions of the 3 components of the B-cell co-receptor?

1. CD21 (or CR2)
2. CD19
3. CD81

Answer 3

1. CD21 or CR2 - recognizes iC3b and C3d on pathogens w/ CR1
2. CD19 - signaling portion
3. CD81 - brings CD19 to the surface; organies B-cell and co-receptor interaction

Question 4

What is the function of CR1 on the surface of B-cells?

Answer 4

Binds to C3b on pathogen and facilitates its cleavage by factor I to iC3b and C3d

Question 5

Once BCR and co-receptor engage the pathogen, _____ phosphorylates CD19 which leads to alterations in gene expression on B-cells

Answer 5

Lyn on the surface of Igα

Question 6

What is the function of follicular dendritic cells (FDCs)

Answer 6

Stromal cells that present antigen for naive B-cells in secondary lymphoid organs

Question 7

Naive B-cells are attracted to the lymph node by ________ and into the B-cell follicle by _______.

Answer 7

1. CCL21 and CCL19
2. CXCL13

Question 8

T_FH cells secrete ______, which drives B-cells away from CXCL13 to set up alignment with T-cells

Answer 8

CCR7

Question 9

If a conjugate pair between T_FH and B cells, T_FH-cells are induced to express CD40 ligand to bind CD40 on B-cells and induce transcription of ______ and ______ to form the synapse.

Answer 9

NF-κB and ICAM-1

Question 10

Why is CR2 on B-cells so long?

Answer 10

Allows it to “fish” for antigen

Question 11

_____ is a transcription factor that induces B-cells to stop dividing and increase Ig chain synthesis and secretion

Answer 11

BLIMP-1

Question 12

True or false. All B-cells are fated to become plasma cells.

Answer 12

False. Some move to primary follicles of B-cell area with T_FH attached

Question 13

Interaction between TFH and B-cells at CD40 causes production of _____, a transcription factor essential for hypermutation and isotype switching.

Answer 13

AID

Question 14

What is the function of each zone of the germinal center?

Answer 14

• Mantle zone: area where naive B-cells pass through lymph node
• Dark zone: compared area of densly-packed centroblasts
• Light zone: low density of centocytes and high density of FDCs and T_FH cells

Question 15

What are centrocytes?

Answer 15

• Slow dividing B-cells waiting to encounter antigen bound to T_FH cells
• Already finished hypermutation and isotype switching

Question 16

Do plasma cells live longer in the lymph node or in bone marrow?

Answer 16

Bone marrow

Question 17

During infection, what cytokine is produced by T_FH cells to induce centrocytes to differentiate into plasma cells?

Answer 17

IL-10

Question 18

As an infection clears, what cytokine is produced by T_FH cells to induce centrocytes to become memory B-cells?

Answer 18

• IL-4
• Overpowers IL-10

Question 19

Which Ig is responsible for binding microorganisms/particulate antigens and activating the classical pathway of complement activation?

Answer 19

IgM

Question 20

Dimeric IgA is synthesized in _____

Answer 20

patches of mucosal-associated lymphoid tissue (MALT)

Question 21

_____ are high-affinity antibodies that prevent microbial attachment to target cells

Answer 21

Neutralizing antibodies

Question 22

To neutralize, an antibody must…. (3)

Answer 22

1. Be high affinity
2. Bind irreversibly
3. Penetrate tissue to reach toxin

Question 23

How does the immune system expel pathogens from the respiratory and GI tract?

Answer 23

• IgE binds to mast cells
• Mast cells secrete mediators that cause sneezing, vomiting, coughing, diarrhea (etc)

Question 24

IgG and monomeric IgA prevent ______

Answer 24

• Blood-borne infections
• Spread of microorganisms