1. What is the clonal selection theory?

A. Each T cell bears multiple types of antigen receptors

B. Each B cell bears a single type of Ig receptor and forms identical clones after activation

C. All B cells recognize the same antigen

D. Plasma cells have many different receptors

B. Each B cell bears a single type of Ig receptor and forms identical clones after activation

2. Why is the clonal selection theory relevant?

A. Explains innate immunity

B. Explains why antibodies are nonspecific

C. Explains the formation of memory cells for faster secondary responses

D. Describes antigen presentation

C. Explains the formation of memory cells for faster secondary responses

3. What is a plasma cell?

A. A B cell that secretes cytokines

B. A B cell that secretes antibodies

C. A naïve B cell in bone marrow

D. A macrophage in the spleen

B. A B cell that secretes antibodies

4. Which mature B cell type participates in germinal center reactions and shows somatic hypermutation?

A. B1 cell

B. MZB cell

C. B2 cell

D. Plasma cell

B. MZB cell

5. Which chemokines recruit B cells to secondary lymphoid tissues?

A. IL-4 and IL-5

B. CCL19 and CCL21

C. TNF and IL-1

D. CXCL10 and CXCL11

B. CCL19 and CCL21

6. Which structure secretes CXCL13 and holds antigen like flypaper?

A. Dendritic cell

B. Follicular dendritic cell (FDC)

C. Plasma cell

D. B1 cell

B. Follicular dendritic cell (FDC)

7. What is BAFF and its role?

A. B-cell activating factor; promotes B cell activation and survival

B. A cytokine that inhibits T cell activity

C. A surface receptor on macrophages

D. A transcription factor in plasma cells

A. B-cell activating factor; promotes B cell activation and survival

8. What is the Fibroblastic Reticular Cell Conduit (FRCC) system?

A. Antibody transport system

B. Channel that allows small antigens to flow through lymph node

C. Site of macrophage development

D. Cytokine signaling pathway

B. Channel that allows small antigens to flow through lymph node

9. Which of the following describes a lipid raft?

A. Soluble protein cluster in cytoplasm

B. Cholesterol- and sphingolipid-rich membrane region involved in signaling

C. Cytoskeletal filament

D. Vesicle carrying MHC molecules

B. Cholesterol- and sphingolipid-rich membrane region involved in signaling

10. What is the role of Igα/Igβ in BCR signaling?

A. Bind antigen directly

B. Anchor the BCR to the membrane

C. Transduce the signal through ITAM phosphorylation

D. Inhibit the B cell response

C. Transduce the signal through ITAM phosphorylation

11. What are the costimulatory molecules in the B cell response?

A. CD3, CD4, CD8

B. CD19, CD21, CD81

C. MHC I, MHC II

D. CD28, B7

B. CD19, CD21, CD81

12. What are the three cell types required for a good B cell response?

A. FDC, B cell, activated CD4+ T cell

B. Plasma cell, macrophage, dendritic cell

C. NK cell, macrophage, B cell

D. Neutrophil, dendritic cell, plasma cell

A. FDC, B cell, activated CD4+ T cell

13. What is a cognate T–B cell interaction?

A. Two unrelated cells binding randomly

B. A B and T cell that recognize different epitopes

C. A B and T cell that recognize the same antigen epitope

D. A B cell activating a CD8+ T cell

C. A B and T cell that recognize the same antigen epitope

14. Which interaction is crucial for B cell activation and class switching?

A. CD28/B7

B. CD40/CD40L

C. MHC I/CD8

D. ICAM/LFA-1

B. CD40/CD40L

15. What cytokine signal determines the type of isotype produced during class switching?

A. IL-10

B. IL-13

C. IFN-γ

D. TNF-α

B. IL-13

16. What enzyme initiates somatic hypermutation and class switch recombination?

A. DNA polymerase

B. Activation-induced deaminase (AID)

C. RNA polymerase

D. DNase

B. Activation-induced deaminase (AID)

17. During somatic hypermutation, AID converts what base to what base?

A. Adenine → Guanine

B. Cytosine → Uracil

C. Thymine → Adenine

D. Guanine → Cytosine

B. Cytosine → Uracil

18. Which zone of the germinal center is densely packed with proliferating B cells?

A. Light zone

B. Dark zone

C. B cell zone

D. T cell zone

B. Dark zone

19. Which statement about T-dependent B cell responses is correct?

A. Occurs without T cell help

B. Requires T cell recognition of same antigen epitope

C. Only produces IgM

D. Occurs only in the thymus

B. Requires T cell recognition of same antigen epitope

20. Which type of antigen typically elicits a T-independent B cell response?

A. Soluble protein

B. Bacterial polysaccharide or cell wall component

C. Viral peptide

D. Fungal glycoprotein

B. Bacterial polysaccharide or cell wall component

21. Germinal center

Site of somatic hypermutation and class switching

22. FDC

Holds antigen and secretes CXCL13

23. plasma cell

Secretes antibody, no longer divides

24. plasmablast

Early antibody-secreting B cell that can still divide

25. TFH cell

Provides help for B cell maturation and class switching

26. Describe the role of chemokines (CCL19, CCL21, CXCL13) in B cell migration and activation.

CCL19/CCL21 recruit B cells to T cell zone via CCR7; CXCL13 attracts B cells into follicles via CXCR5.

27. What is the purpose of a B cell acting as an antigen-presenting cell (APC)?

To present antigen on MHC II to a cognate T cell for activation and class switching

28. Define clustering of the BCR and explain what causes it.

Antigen binding causes BCRs to cluster into lipid rafts, enhancing signaling

29. Explain the difference between FDCs and conventional dendritic cells.

FDCs hold antigen; conventional DCs process and present antigen

30. List the three SMAC regions and their purposes.

cSMAC = signaling; pSMAC = adhesion; dSMAC = actin support

31. What happens to a B cell that fails to find its cognate antigen in the lymph node?

It exits lymph node and reenters circulation.

32. Explain the difference between plasma cells and plasmablasts.

Plasma cells secrete antibody but do not divide; plasmablasts secrete and still divide.

33. What two major processes occur in the germinal center?

Somatic hypermutation (affinity maturation) and class switching.

34. Explain how somatic hypermutation improves antibody affinity.

Introduces mutations in variable region; selects B cells with stronger antigen binding.

35. Describe the difference between T-dependent and T-independent B cell responses.

TD = requires T cell help and class switching; TI = activated by polysaccharide antigens, mostly IgM response.