Introduction: Hypersensitivity reactions and immune regulation are core immunology topics for B.Pharm students, linking pathophysiology to rational pharmacotherapy. This concise overview covers Type I, II, III and IV hypersensitivity mechanisms, roles of IgE, complement, immune complexes, T cells, cytokines and regulatory T cells. Emphasis is on clinical manifestations, diagnostic tests, drug-induced hypersensitivity, and therapeutic strategies including antihistamines, corticosteroids, epinephrine, monoclonal antibodies and immunosuppressants. Understanding immune checkpoints, antigen presentation, Fc receptors and complement pathways helps predict adverse drug reactions and optimize treatment. Keywords: hypersensitivity reactions, immune regulation, Type I–IV, IgE, cytokines, complement, pharmacotherapy, diagnostics, B.Pharm. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which immunoglobulin class primarily mediates Type I (immediate) hypersensitivity?
- IgG
- IgM
- IgA
- IgE
Correct Answer: IgE
Q2. Which cell type is the main effector cell releasing histamine in Type I hypersensitivity?
- Macrophage
- Neutrophil
- Mast cell
- CD8+ T cell
Correct Answer: Mast cell
Q3. Which mechanism best describes Type II hypersensitivity?
- Immune complex deposition in vessel walls
- Antibody-mediated cytotoxicity against cell-surface antigens
- T-cell mediated delayed hypersensitivity
- IgE-mediated mast cell degranulation
Correct Answer: Antibody-mediated cytotoxicity against cell-surface antigens
Q4. A classic example of Type III hypersensitivity is:
- Myasthenia gravis
- Systemic lupus erythematosus (immune complex mediated)
- Anaphylaxis to bee sting
- Contact dermatitis to poison ivy
Correct Answer: Systemic lupus erythematosus (immune complex mediated)
Q5. Which test is commonly used to detect immediate IgE-mediated hypersensitivity to drugs or allergens?
- Patch test
- Skin prick test
- Direct Coombs test
- ANA test
Correct Answer: Skin prick test
Q6. Complement activation via immune complexes primarily involves which pathway?
- Lectin pathway only
- Classical pathway
- Intrinsic coagulation pathway
- Alternative pathway exclusively
Correct Answer: Classical pathway
Q7. Which cytokine is most important for class switching to IgE during allergic sensitization?
- IFN-gamma
- IL-4
- IL-17
- TGF-beta
Correct Answer: IL-4
Q8. In drug-induced hemolytic anemia, which test detects antibodies bound to red blood cells?
- ELISA for complement C3
- Indirect Coombs test
- Direct Coombs test
- Skin biopsy
Correct Answer: Direct Coombs test
Q9. Which hypersensitivity type is primarily T cell–mediated and responsible for contact dermatitis?
- Type I
- Type II
- Type III
- Type IV
Correct Answer: Type IV
Q10. Which therapeutic agent specifically targets IgE and is used in severe allergic asthma?
- Infliximab
- Omalizumab
- Rituximab
- Adalimumab
Correct Answer: Omalizumab
Q11. Which immune regulator cell subset suppresses excessive immune responses and maintains tolerance?
- Th17 cells
- CD8+ cytotoxic T cells
- Regulatory T cells (Tregs)
- Follicular helper T cells
Correct Answer: Regulatory T cells (Tregs)
Q12. In Type II hypersensitivity, antibody-dependent cellular cytotoxicity (ADCC) is mediated primarily through Fc receptors on:
- B cells
- Neutrophils only
- Natural killer (NK) cells
- Platelets
Correct Answer: Natural killer (NK) cells
Q13. Which lab marker indicates complement consumption in immune complex disease?
- Elevated C3 and C4
- Decreased C3 and C4
- Elevated IgA only
- Normal complement with high CRP
Correct Answer: Decreased C3 and C4
Q14. Which antibiotic is most commonly associated with IgE-mediated anaphylaxis?
- Penicillin
- Tetracycline
- Vancomycin
- Ciprofloxacin
Correct Answer: Penicillin
Q15. Which mediator causes vascular smooth muscle relaxation and increased vascular permeability in immediate hypersensitivity?
- IL-2
- Histamine
- Complement C5a
- Interferon-alpha
Correct Answer: Histamine
Q16. A positive patch test primarily detects which type of hypersensitivity?
- Immediate IgE-mediated hypersensitivity
- Cell-mediated delayed hypersensitivity (Type IV)
- Immune complex-mediated hypersensitivity
- Autoantibody-mediated cytotoxicity
Correct Answer: Cell-mediated delayed hypersensitivity (Type IV)
Q17. Which drug class is first-line for acute management of anaphylaxis?
- Systemic corticosteroids
- H1 antihistamines
- Epinephrine (intramuscular)
- Leukotriene receptor antagonists
Correct Answer: Epinephrine (intramuscular)
Q18. Immune complex deposition in glomeruli leading to nephritis is most characteristic of which immunologic process?
- Type I hypersensitivity
- Type II hypersensitivity
- Type III hypersensitivity
- Type IV hypersensitivity
Correct Answer: Type III hypersensitivity
Q19. Which receptor on mast cells binds the Fc portion of IgE and is critical for allergic sensitization?
- FcγRI
- FcεRI
- CD28
- TLR4
Correct Answer: FcεRI
Q20. Which cytokine profile is associated with Th1 responses that promote macrophage activation and Type IV hypersensitivity?
- IL-4 and IL-5
- IL-17 and IL-22
- IFN-gamma and IL-2
- IL-10 and TGF-beta
Correct Answer: IFN-gamma and IL-2
Q21. Which diagnostic assay measures specific IgE in serum against defined allergens?
- ELISA for specific IgE
- Direct Coombs test
- PCR for HLA alleles
- Complete blood count only
Correct Answer: ELISA for specific IgE
Q22. Drug desensitization protocols are indicated when:
- A nonessential drug causes mild rash
- An essential medication causes an immediate hypersensitivity but no alternatives exist
- The patient refuses all medications
- The hypersensitivity is T cell–mediated severe skin reaction (SJS/TEN)
Correct Answer: An essential medication causes an immediate hypersensitivity but no alternatives exist
Q23. Which HLA association is known to increase risk of severe cutaneous adverse drug reactions to carbamazepine in some populations?
- HLA-B*57:01
- HLA-B*15:02
- HLA-DR4
- HLA-A*02:01
Correct Answer: HLA-B*15:02
Q24. Which monoclonal antibody targets TNF-alpha and can modify immune responses in autoimmune conditions?
- Omalizumab
- Infliximab
- Rituximab
- Bevacizumab
Correct Answer: Infliximab
Q25. Which process helps clear circulating immune complexes and prevents Type III hypersensitivity?
- Fc receptor-mediated phagocytosis in spleen and liver
- Inhibition of complement C1q only
- Production of IgE antibodies
- Th2 polarization exclusively
Correct Answer: Fc receptor-mediated phagocytosis in spleen and liver
Q26. Which antihistamine property is most desirable for rapid relief of acute allergic rhinitis symptoms?
- High anticholinergic sedation
- Strong H1 receptor antagonism with rapid onset
- Exclusive leukotriene inhibition
- Corticosteroid receptor activation
Correct Answer: Strong H1 receptor antagonism with rapid onset
Q27. Chronic Type IV hypersensitivity in tuberculosis is mediated predominantly by which cell type?
- B cells producing IgG
- CD4+ Th1 cells activating macrophages
- Mast cells releasing histamine
- Neutrophils forming pus
Correct Answer: CD4+ Th1 cells activating macrophages
Q28. Which lab finding suggests an allergic (Type I) reaction rather than an autoimmune cytotoxic reaction?
- High titers of anti-neutrophil cytoplasmic antibodies (ANCA)
- Elevated serum tryptase and histamine
- Positive direct Coombs test
- Low complement with immune complexes
Correct Answer: Elevated serum tryptase and histamine
Q29. Which pharmacologic agent blocks leukotriene receptors and is useful in aspirin-exacerbated respiratory disease and asthma?
- Montelukast
- Prednisone
- Diphenhydramine
- Propranolol
Correct Answer: Montelukast
Q30. Immune checkpoint molecules such as CTLA-4 and PD-1 regulate immune responses by:
- Promoting constant activation of T cells
- Providing inhibitory signals that limit T-cell activation
- Directly producing antibodies against allergens
- Enhancing IgE class switching
Correct Answer: Providing inhibitory signals that limit T-cell activation
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com