Cells and organs of the immune system MCQs With Answer

Introduction

This blog provides a focused question bank on cells and organs of the immune system tailored for M.Pharm students. It emphasizes cellular phenotypes, anatomical sites of lymphopoiesis, antigen presentation, lymphoid microenvironments and trafficking signals relevant to immunopharmacology and vaccine development. Each MCQ targets core concepts such as hematopoiesis, thymic selection, splenic architecture, germinal centers, mucosal-associated lymphoid tissues, antigen-presenting cell subsets, and effector cell functions. Detailed options test mechanistic understanding, receptor–ligand interactions and clinical implications for drug design. Use these questions for revision, self-assessment, or classroom discussion; answers are provided to reinforce learning and identify areas requiring deeper study. Complete explanations are recommended to consolidate pharmacological applications and experimental approaches.

Q1. Which bone marrow cell type serves as the primary source of long-term hematopoietic stem cells (HSCs) that give rise to lymphoid and myeloid lineages?

• Common lymphoid progenitor (CLP)
• Long-term hematopoietic stem cell (LT-HSC) characterized by CD34+CD38− phenotype
• Multipotent progenitor (MPP)
• Granulocyte–macrophage progenitor (GMP)

Correct Answer: Long-term hematopoietic stem cell (LT-HSC) characterized by CD34+CD38− phenotype

Q2. During T cell development in the thymus, which process eliminates T cells that bind self-MHC with very high affinity to prevent autoreactivity?

• Positive selection
• Clonal expansion
• Negative selection (central tolerance)
• Somatic hypermutation

Correct Answer: Negative selection (central tolerance)

Q3. Which splenic region is primarily involved in filtering blood-borne antigens and supporting B cell maturation in germinal centers?

• Red pulp
• Marginal zone
• White pulp, particularly the follicles and germinal centers
• Trabecular sinus

Correct Answer: White pulp, particularly the follicles and germinal centers

Q4. Which chemokine receptor is critical for naive T cell homing to lymph nodes via high endothelial venules (HEVs)?

• CCR5
• CCR7
• CXCR3
• CXCR5

Correct Answer: CCR7

Q5. Which antigen-presenting cell subset is most specialized for cross-presentation of exogenous antigens on MHC class I to CD8+ T cells?

• Follicular dendritic cells
• Conventional type 2 dendritic cells (cDC2)
• Plasmacytoid dendritic cells
• Conventional type 1 dendritic cells (cDC1)

Correct Answer: Conventional type 1 dendritic cells (cDC1)

Q6. Which mucosal-associated lymphoid tissue (MALT) structure in the small intestine contains specialized M cells that sample luminal antigens?

• Peyer’s patches
• Appendix
• Lymphoid follicles in the spleen
• Palatine tonsils

Correct Answer: Peyer’s patches

Q7. Which cytokine is most important for early B cell development and survival in the bone marrow microenvironment?

• Interleukin-7 (IL-7)
• Interferon-gamma (IFN-γ)
• Interleukin-4 (IL-4)
• Granulocyte-macrophage colony-stimulating factor (GM-CSF)

Correct Answer: Interleukin-7 (IL-7)

Q8. Which cell type in lymph nodes presents intact antigen complexes to B cells within germinal centers to promote affinity maturation?

• Conventional dendritic cells
• Follicular dendritic cells
• Macrophages
• Plasma cells

Correct Answer: Follicular dendritic cells

Q9. Which adhesion molecule mediates the initial rolling of leukocytes along high endothelial venules during lymphocyte homing?

• ICAM-1
• VLA-4 (α4β1 integrin)
• L-selectin (CD62L)
• VCAM-1

Correct Answer: L-selectin (CD62L)

Q10. Which innate immune cell is the most abundant circulating phagocyte and first responder to bacterial infection?

• Monocyte
• Neutrophil
• Natural killer (NK) cell
• Eosinophil

Correct Answer: Neutrophil

Q11. In the thymus, which cell type provides antigen presentation and mediates negative selection through ectopic expression of peripheral tissue antigens (via AIRE)?

• Medullary thymic epithelial cells (mTECs)
• Thymic dendritic cells
• Cortical thymic epithelial cells (cTECs)
• Hassall’s corpuscle macrophages

Correct Answer: Medullary thymic epithelial cells (mTECs)

Q12. Which splenic cell population is specialized to capture encapsulated bacterial polysaccharides and mount TI (T-cell independent) B cell responses?

• Follicular B cells (B-2)
• Marginal zone B cells
• Plasma cells
• Tfh cells

Correct Answer: Marginal zone B cells

Q13. Which receptor on macrophages recognizes the Fc portion of IgG and facilitates antibody-dependent cellular phagocytosis?

• Toll-like receptor 4 (TLR4)
• CR1 complement receptor
• Fcγ receptor (FcγR)
• FcεRI

Correct Answer: Fcγ receptor (FcγR)

Q14. Which organ is the primary site for central tolerance induction of B cells and negative selection against self-reactive B cell receptors?

• Bone marrow
• Thymus
• Spleen
• Lymph node

Correct Answer: Bone marrow

Q15. Which innate lymphoid cell (ILC) group mirrors Th2 responses and contributes to mucosal immunity and allergic inflammation?

• ILC1
• ILC2
• ILC3
• Natural killer T (NKT) cells

Correct Answer: ILC2

Q16. Which cell surface molecule is used as the classic marker of naive B cells and is important for B-cell receptor signaling modulation?

• CD3
• CD19
• CD56
• CD14

Correct Answer: CD19

Q17. Cross-presentation by dendritic cells allows presentation of exogenous antigens on MHC class I; which intracellular pathway is primarily involved?

• Endosomal MHC II loading pathway
• Cytosolic proteasome-dependent processing and TAP-dependent peptide transport
• Autophagosome-mediated MHC II cross-loading
• Lysosomal degradation without proteasome involvement

Correct Answer: Cytosolic proteasome-dependent processing and TAP-dependent peptide transport

Q18. Which organ contains white pulp organized around central arterioles where T cell zones (periarteriolar lymphoid sheaths) are found?

• Lymph node
• Bone marrow
• Spleen
• Thymus

Correct Answer: Spleen

Q19. Which pattern-recognition receptor family, expressed on macrophages and dendritic cells, detects bacterial lipopolysaccharide (LPS) and initiates strong innate responses?

• Toll-like receptor 4 (TLR4)
• RIG-I-like receptors (RLRs)
• NOD-like receptor NOD2
• Toll-like receptor 3 (TLR3)

Correct Answer: Toll-like receptor 4 (TLR4)

Q20. Which cytokine produced by stromal cells in the thymus is essential for early T cell progenitor survival and proliferation?

• IL-2
• IL-7
• IL-10
• TNF-α

Correct Answer: IL-7

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