Introduction
Mechanisms and treatment of hypersensitivity MCQs With Answer is a focused quiz designed for M.Pharm students preparing for advanced immunology and clinical pharmacology examinations. This collection emphasizes detailed mechanistic understanding of the four types of hypersensitivity reactions, the cellular and molecular mediators involved, and evidence-based therapeutic strategies including emergency management, pharmacologic interventions, biologics, immunotherapy and procedural options. Each question targets application-level knowledge—linking pathophysiology to drug mechanisms, diagnostic tools and treatment rationale—so students can confidently tackle real-world clinical scenarios and exam-style problems. Use these MCQs for self-assessment, revision, and to identify areas needing deeper study.
Q1. What is the primary immunologic event that triggers an immediate Type I hypersensitivity reaction?
- Crosslinking of antigen-specific IgE bound to FcεRI receptors on mast cells and basophils causing degranulation
- Deposition of antigen–antibody immune complexes in vessel walls and tissues activating complement
- Complement-mediated lysis of target cells following IgG binding to surface antigens
- CD8+ T-cell–mediated cytotoxicity against antigen-bearing host cells
Correct Answer: Crosslinking of antigen-specific IgE bound to FcεRI receptors on mast cells and basophils causing degranulation
Q2. In the pre-hospital management of severe anaphylaxis, which is the first-line drug and route of administration?
- Intramuscular epinephrine into the lateral thigh
- Intravenous hydrocortisone bolus
- Oral second-generation antihistamine
- Nebulized salbutamol (albuterol)
Correct Answer: Intramuscular epinephrine into the lateral thigh
Q3. Which group of mediators produced by activated mast cells is most responsible for sustained bronchoconstriction in allergic asthma?
- Cysteinyl leukotrienes (LTC4, LTD4, LTE4)
- Prostaglandin I2 (prostacyclin)
- Platelet-activating factor (PAF)
- Histamine acting on H2 receptors
Correct Answer: Cysteinyl leukotrienes (LTC4, LTD4, LTE4)
Q4. What is the mechanism of action of omalizumab in allergic asthma?
- Monoclonal antibody that binds circulating IgE and prevents IgE binding to FcεRI on effector cells
- Anti–IL-5 monoclonal antibody that reduces eosinophil survival
- IL-4 receptor antagonist that blocks Th2 signaling
- Anti–TNF-α antibody that inhibits systemic inflammation
Correct Answer: Monoclonal antibody that binds circulating IgE and prevents IgE binding to FcεRI on effector cells
Q5. Which of these diseases is a classic example of a Type II (antibody-mediated) hypersensitivity?
- Myasthenia gravis caused by autoantibodies against the acetylcholine receptor
- Systemic lupus erythematosus driven primarily by circulating immune complexes
- Allergic rhinitis due to IgE-mediated nasal mucosal mast cell activation
- Contact dermatitis mediated by sensitized T lymphocytes
Correct Answer: Myasthenia gravis caused by autoantibodies against the acetylcholine receptor
Q6. Which immunosuppressive drug inhibits calcineurin to block NFAT activation and reduce IL-2 transcription in T cells?
- Cyclosporine
- Methotrexate
- Azathioprine
- Prednisone
Correct Answer: Cyclosporine
Q7. What is the central pathogenic mechanism in Type III hypersensitivity reactions?
- Deposition of antigen–antibody immune complexes in tissues with complement activation and neutrophil recruitment
- IgE-mediated mast cell degranulation causing vasodilation and increased permeability
- Autoantibody-mediated complement lysis of cells via the membrane attack complex
- CD8+ T-cell–mediated apoptosis of target cells
Correct Answer: Deposition of antigen–antibody immune complexes in tissues with complement activation and neutrophil recruitment
Q8. Serum sickness is typically a delayed immune-complex reaction. What is the usual time window for symptom onset after exposure?
- 1–2 weeks after exposure
- Within minutes of exposure
- 48–72 hours after exposure
- Several months after exposure
Correct Answer: 1–2 weeks after exposure
Q9. Which diagnostic test directly measures circulating allergen-specific IgE antibodies?
- Radioallergosorbent test (RAST) / specific IgE immunoassay
- Complete blood count with differential
- Serum tryptase measured weeks after exposure
- Pulmonary function testing with bronchodilator response
Correct Answer: Radioallergosorbent test (RAST) / specific IgE immunoassay
Q10. Contact dermatitis from nickel is primarily mediated by which immune mechanism?
- Th1-type CD4+ T-cell–mediated delayed (Type IV) hypersensitivity with macrophage activation
- IgE-mediated mast cell degranulation (Type I)
- Immune complex deposition in the skin (Type III)
- Complement-mediated cell lysis following antibody binding (Type II)
Correct Answer: Th1-type CD4+ T-cell–mediated delayed (Type IV) hypersensitivity with macrophage activation
Q11. Which biologic therapy specifically targets IL-5 to reduce eosinophil counts in severe eosinophilic asthma?
- Mepolizumab
- Omalizumab
- Rituximab
- Infliximab
Correct Answer: Mepolizumab
Q12. For persistent moderate-to-severe allergic rhinitis, which long-term therapy is considered most effective at controlling nasal inflammation?
- Intranasal corticosteroids
- Oral second-generation antihistamines
- Subcutaneous allergen immunotherapy (SCIT)
- Leukotriene receptor antagonists
Correct Answer: Intranasal corticosteroids
Q13. Which is a principal mechanism by which intravenous immunoglobulin (IVIG) exerts therapeutic benefit in certain antibody-mediated autoimmune diseases?
- Saturation/blockade of Fc receptors and neutralization of pathogenic antibodies via anti‑idiotypic interactions
- Direct cytotoxic elimination of autoreactive T cells
- Selective inhibition of IL-17 production by Th17 cells
- Specific depletion of B cells through complement activation
Correct Answer: Saturation/blockade of Fc receptors and neutralization of pathogenic antibodies via anti‑idiotypic interactions
Q14. Graft-versus-host disease following allogeneic bone marrow transplant is primarily classified as which hypersensitivity type?
- Type IV (cell-mediated delayed hypersensitivity)
- Type I (IgE-mediated immediate hypersensitivity)
- Type II (antibody-mediated cytotoxic hypersensitivity)
- Type III (immune complex-mediated hypersensitivity)
Correct Answer: Type IV (cell-mediated delayed hypersensitivity)
Q15. Which complement fragments are known as anaphylatoxins and contribute to mast cell activation and chemotaxis?
- C3a and C5a
- C3b and C4b
- C1q and C2a
- Factor B and Factor D
Correct Answer: C3a and C5a
Q16. Allergen desensitization (allergen immunotherapy) induces clinical tolerance primarily through which immunologic changes?
- Generation of regulatory T cells and production of blocking IgG4 antibodies with reduced IgE responses
- Permanent depletion of B cells via complement-mediated lysis
- Immediate suppression of mast cell numbers in tissues
- Induction of a strong Th17 response to outcompete Th2 cells
Correct Answer: Generation of regulatory T cells and production of blocking IgG4 antibodies with reduced IgE responses
Q17. In suspected heparin-induced thrombocytopenia (HIT) with thrombosis (Type II hypersensitivity to heparin–PF4), what is the recommended immediate therapeutic step?
- Discontinue all heparin products and initiate a non-heparin anticoagulant such as argatroban
- Administer platelet transfusion immediately to raise platelet count
- Start warfarin monotherapy while continuing heparin
- Increase the heparin dose and monitor closely
Correct Answer: Discontinue all heparin products and initiate a non-heparin anticoagulant such as argatroban
Q18. Which diagnostic pattern supports a diagnosis of immune complex–mediated vasculitis on tissue biopsy?
- Granular (“lumpy-bumpy”) deposition of immunoglobulin and complement with low serum complement levels
- Linear deposition of IgG along basement membranes with normal complement levels
- Predominant CD8+ T-cell infiltrate without immune-complex deposition
- Absence of inflammatory infiltrate but presence of fibrinoid necrosis only
Correct Answer: Granular (“lumpy-bumpy”) deposition of immunoglobulin and complement with low serum complement levels
Q19. Which targeted biologic blocks IL-4 and IL-13 signaling and is effective in atopic dermatitis and certain atopic conditions?
- Dupilumab (anti–IL-4Rα monoclonal antibody)
- Omalizumab (anti-IgE monoclonal antibody)
- Ustekinumab (anti–IL-12/23 monoclonal antibody)
- Etanercept (TNF receptor fusion protein)
Correct Answer: Dupilumab (anti–IL-4Rα monoclonal antibody)
Q20. Which agent acts as a mast cell stabilizer to prevent degranulation and is used prophylactically in allergic conditions?
- Cromolyn sodium
- Montelukast
- Theophylline
- Zafirlukast
Correct Answer: Cromolyn sodium
