Understanding the types of immunity—humoral and cellular—is essential for B.Pharm students studying immunology, pharmacology and vaccine development. Humoral immunity, mediated by B cells, plasma cells and antibodies (IgG, IgM, IgA, IgE, IgD), neutralizes extracellular pathogens and toxins. Cellular immunity, driven by T cells (CD4+, CD8+), antigen-presenting cells (APCs), macrophages and cytokines, eliminates infected or transformed cells. Core concepts include antigen presentation, MHC I/II pathways, clonal selection, class-switch recombination, memory cell formation, opsonization, and cytotoxic mechanisms. This knowledge underpins rational use of vaccines, monoclonal antibodies and immunosuppressants in clinical practice. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which cells are the primary effectors that secrete antibodies in humoral immunity?
- B cells
- Plasma cells
- T helper cells
- Natural killer cells
Correct Answer: Plasma cells
Q2. Which immunoglobulin class readily crosses the placenta to provide passive immunity to the fetus?
- IgM
- IgA
- IgG
- IgE
Correct Answer: IgG
Q3. MHC class I molecules present peptides primarily to which lymphocyte subset?
- CD4+ T helper cells
- CD8+ cytotoxic T cells
- B cells
- NK cells
Correct Answer: CD8+ cytotoxic T cells
Q4. Exogenous antigens processed in endosomes and presented on MHC class II activate which cells?
- CD8+ T cells
- CD4+ T helper cells
- Plasma cells
- Neutrophils
Correct Answer: CD4+ T helper cells
Q5. Which cytokine is a key signature product of Th1 responses and activates macrophages?
- IL-4
- IL-10
- IFN-gamma
- IL-17
Correct Answer: IFN-gamma
Q6. A Th2-dominated response promotes class switching to which antibody associated with allergic responses?
- IgG
- IgA
- IgM
- IgE
Correct Answer: IgE
Q7. Which complement pathway is triggered by antigen–antibody complexes?
- Alternative pathway
- Lectin pathway
- Classical pathway
- Properdin pathway
Correct Answer: Classical pathway
Q8. Which complement fragment is most important for opsonization and enhancing phagocytosis?
- C3a
- C3b
- C5a
- C9
Correct Answer: C3b
Q9. Which cells mediate target cell killing by releasing perforin and granzymes?
- CD4+ T helper cells
- Plasma cells
- CD8+ cytotoxic T lymphocytes
- B cells
Correct Answer: CD8+ cytotoxic T lymphocytes
Q10. Which professional antigen-presenting cell is most efficient at priming naïve T cells?
- Neutrophil
- Erythrocyte
- Dendritic cell
- Fibroblast
Correct Answer: Dendritic cell
Q11. Affinity maturation of antibodies occurs primarily in which anatomical site?
- Bone marrow medulla
- Thymic cortex
- Germinal centers of lymph nodes
- Spleen red pulp
Correct Answer: Germinal centers of lymph nodes
Q12. Memory B cells and long-lived plasma cells are generated mainly through which process?
- Clonal anergy
- Germinal center reaction
- Complement fixation
- Immediate hypersensitivity
Correct Answer: Germinal center reaction
Q13. Which is an example of passive immunity?
- Receiving killed vaccine
- Administration of immunoglobulin (IVIG)
- Activation of naïve B cells
- Natural infection leading to immunity
Correct Answer: Administration of immunoglobulin (IVIG)
Q14. Which scenario best describes active immunity?
- Maternal IgG transferred to infant
- Injection of antitoxin antibodies
- Immune response after vaccination
- Administration of monoclonal antibodies
Correct Answer: Immune response after vaccination
Q15. Which type of vaccine most strongly stimulates both humoral and cellular immunity, including CD8+ T cell responses?
- Inactivated (killed) vaccines
- Subunit vaccines
- Live attenuated vaccines
- Toxoid vaccines
Correct Answer: Live attenuated vaccines
Q16. Class-switch recombination in B cells changes which property of antibodies?
- Antigen specificity
- Variable region DNA sequence
- Isotype (constant region) such as IgM to IgG
- Antigen binding affinity only
Correct Answer: Isotype (constant region) such as IgM to IgG
Q17. Fcγ receptors mainly bind which part of an antibody to mediate opsonization and ADCC?
- Fab region
- Hinge region
- Fc region of IgG
- Carbohydrate side chains only
Correct Answer: Fc region of IgG
Q18. Exogenous antigen processing for MHC II presentation involves which intracellular compartment?
- Proteasome in cytosol
- Endoplasmic reticulum lumen exclusively
- Endosomal/lysosomal compartments
- Mitochondrial matrix
Correct Answer: Endosomal/lysosomal compartments
Q19. Which innate lymphocyte detects cells with reduced MHC class I expression (‘missing self’)?
- CD4+ T cells
- Natural killer cells
- B cells
- Neutrophils
Correct Answer: Natural killer cells
Q20. Which immunosuppressive drug inhibits calcineurin and T-cell activation by blocking NFAT signaling?
- Azathioprine
- Cyclophosphamide
- Cyclosporine
- Mycophenolate mofetil
Correct Answer: Cyclosporine
Q21. During a primary humoral immune response, which antibody is produced first by naïve B cells?
- IgG
- IgA
- IgM
- IgE
Correct Answer: IgM
Q22. Which characteristic best describes a secondary (anamnestic) immune response?
- Slower onset and lower affinity antibodies
- Faster onset with higher affinity IgG due to memory cells
- Exclusive production of IgM without class switching
- Absence of memory B cells
Correct Answer: Faster onset with higher affinity IgG due to memory cells
Q23. Antibody-mediated cell destruction and complement activation against cell-surface antigens is classified as which hypersensitivity type?
- Type I hypersensitivity
- Type II hypersensitivity
- Type III hypersensitivity
- Type IV hypersensitivity
Correct Answer: Type II hypersensitivity
Q24. Which laboratory assay is commonly used to quantify specific antibodies in serum, assessing humoral immunity?
- Western blot for cytokines
- ELISA for specific antibodies
- Flow cytometry for MHC expression only
- Polymerase chain reaction for T cell receptors
Correct Answer: ELISA for specific antibodies
Q25. Intracellular (endogenous) antigens are typically processed and presented on which MHC class?
- MHC class II
- MHC class I
- Helper MHC complex
- MHC class III
Correct Answer: MHC class I
Q26. Effective thymus-dependent B cell activation requires help from which specialized CD4+ T cell subset?
- Th17 cells
- Regulatory T cells (Treg)
- T follicular helper (Tfh) cells
- CD8+ cytotoxic T cells
Correct Answer: T follicular helper (Tfh) cells
Q27. Which cytokine is the principal effector secreted by Th17 cells?
- IL-4
- IL-10
- IL-17
- IFN-alpha
Correct Answer: IL-17
Q28. The process that eliminates self-reactive T cells during thymic development is called what?
- Positive selection
- Somatic hypermutation
- Negative selection
- Class-switch recombination
Correct Answer: Negative selection
Q29. Rituximab, used in certain autoimmune diseases and lymphomas, targets which B-cell surface antigen?
- CD3
- CD19
- CD20
- CD28
Correct Answer: CD20
Q30. Which clinical test is an example of delayed-type hypersensitivity and assesses cell-mediated immunity to mycobacterial antigens?
- ELISA for anti-mycobacterial IgG
- Complement fixation test
- Tuberculin skin test (Mantoux)
- Rapid antigen detection test
Correct Answer: Tuberculin skin test (Mantoux)
