B Lymphocyte Activation and Differentiation

Question 1

B-cells give rise to which cells that secrete antibodies that destroy extracellular pathogens and prevent the spread of intracellular pathogens?

Answer 1

Plasma cells

Question 2

In the bone marrow, B cells developed and generated unique, random ….

Answer 2

BCRs

Question 3

In the bone marrow, which selection did B cells undergo to ensure the survival of non-self-reactive cells?
A. positive selection
B. negative selection
C. both

Answer 3

C. both

Question 4

In the periphery, immature B cells bear which receptors? What do they mature to express?

Answer 4

1. bear Ig receptors
2. express: IgM and IgD

Question 5

How do mature, naive B cells recirculate?

Answer 5

• blood
• draining lymph nodes
• spleen

Question 6

What is occurring in this diagram?

Answer 6

Clonal expansion
- receptor of single specificity
- upon antigen binding, each cell creates a clone

Question 7

What is needed to activate mature, naive B cells?

Answer 7

1. BCR engagement
2. T-dependent (TD) or T-independent (TI) antigen signaling

Question 8

Where do B cells encounter antigens?

Answer 8

• lymph nodes
• spleen

Question 9

Upon B cell activation, what occurs in BCR engagement?

Answer 9

• BCR binds soluble antigen
• Lyn phosphorylates ITAMs on Igα/Igβ

Question 10

T/F. Antigen (Ag) receptor clustering induces internalization and inhibits antigen presentation.

Answer 10

False. Antigen (Ag) receptor clustering induces internalization and antigen presentation.

Question 11

Once B cell signaling begins, the BCR+Ag complexes are:
A. exocytosed
B. endocytosed

Answer 11

B. endocytosed

Question 12

After going through the exogenous pathway, antigen peptide fragments are loaded onto which MHC class?

Answer 12

MHC class II (CD4+)

Question 13

Antigen engagement with B cells upregulates which receptors?

Answer 13

CD40 and CD80/CD86

Question 14

If B cell activation requires the participation of CD4+ helper T cells this is known as which type of response?

Answer 14

T-dependent

Question 15

What are the 3 signals of the TD response?

Answer 15

1. B cell binds to antigen via Ig receptor
   - bound Ag is presented to T helper cell
2. T cells bind to MHC and costimulation occurs
   - CD40 on B cell interacts with CD40L on T cell
3. T cell delivers activating cytokines

Question 16

Activation of B cells that follow direct recognition of determinants shared between microbial species that does not require T helper cells is what kind of response?

Answer 16

T-independent

Question 17

What signal(s) occur in the TI response?

Answer 17

1. Antigen binds to B cells through Ig receptors and PRRs
2. Antigens are opsonized by complements

Question 18

What are the 5 classes of antibody isotypes located on the effector region of the BCR heavy chain?

Answer 18

1. IgM
2. IgD
3. IgA
4. IgE
5. IgG

Question 19

Does class switch recombination (CSR) occur within secondary lymphoid organs after or before antigen contact?

Answer 19

after

Question 20

Where do B cells receive costimulatory signals?

Answer 20

CD40

Question 21

Determine antibody Isotype CSR based on cytokine signaling.
IL-4
IL-5
TGFβ
IFNγ

Answer 21

IL-4: IgG, IgE (Th2, Tfh)
IL-5: IgA (Th2)
TGFβ: IgA, IgG (Treg)
IFNγ: IgG (Th1)

Question 22

Which molecule activates CSR?

Answer 22

AID