Immunology and Allergies Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Immunology and Allergies. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Immunology and Allergies Indian Medical PG Question 1: A 32 year old man presents with a 3-month history of weight loss, night sweats, a productive cough with blood-tinged sputum, anorexia, general malaise, and a low grade fever. A PPD skin test shows > 10 mm of induration. If the area of induration were biopsied, which of the following type of reactive cells would be found?
- A. Eosinophil
- B. T lymphocyte (Correct Answer)
- C. B lymphocyte
- D. Mast cell
Immunology and Allergies Explanation: ***T lymphocyte***
- The clinical picture (weight loss, night sweats, productive cough with blood-tinged sputum, positive PPD) is highly suggestive of **tuberculosis**, a **Type IV hypersensitivity reaction** [1], [2].
- **Type IV hypersensitivity reactions** are cell-mediated, involving the activation of **T lymphocytes**, which migrate to the site of antigen exposure (like a PPD test site or a tuberculous granuloma) and release cytokines, leading to induration and inflammation [1], [2].
*Eosinophil*
- **Eosinophils** are primarily involved in allergic reactions and defense against parasitic infections [3].
- They are not the predominant reactive cells in a **Type IV hypersensitivity** response like that seen in tuberculosis [1].
*Mast cell*
- **Mast cells** play a critical role in immediate hypersensitivity reactions (Type I), releasing histamine and other mediators [4].
- They are not the primary cells involved in the delayed-type hypersensitivity response elicited by tuberculin purified protein derivative (PPD) [2].
*B lymphocyte*
- **B lymphocytes** are responsible for humoral immunity by producing antibodies [3].
- While they contribute to overall immune responses, they are not the main effector cells in a cell-mediated **Type IV hypersensitivity reaction** characteristic of a positive PPD test [1], [2].
**References:**
[1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 173-174.
[2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 218.
[3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 195-196.
[4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210.
Immunology and Allergies Indian Medical PG Question 2: A child has a rash. His family history is positive for asthma. What could be the most probable diagnosis?
- A. Seborrheic dermatitis
- B. Atopic dermatitis (Correct Answer)
- C. Allergic contact dermatitis
- D. Erysipelas
Immunology and Allergies Explanation: ***Atopic dermatitis***
- The presence of a rash in a child with a family history of **asthma** strongly suggests atopic dermatitis, as it is part of the **atopic triad** (eczema, asthma, allergic rhinitis).
- Atopic dermatitis often presents with **erythematous, pruritic patches** and plaques, commonly affecting flexural areas like the antecubital and popliteal fossae, as well as the face and neck in younger children.
*Seborrheic dermatitis*
- This condition typically presents with **greasy, yellowish scales** on an erythematous base, often affecting areas rich in sebaceous glands such as the scalp, face (nasolabial folds), and chest.
- While it can occur in infants, it does not have the strong association with a family history of asthma seen in atopic dermatitis.
*Allergic contact dermatitis*
- This rash results from an **exposure to an allergen**, leading to a localized, erythematous, and pruritic eruption, often with vesicles or bullae, at the site of contact.
- The history does not provide information about a specific allergen exposure, and while it could produce a similar-looking rash, the family history of asthma points more strongly to atopic diathesis.
*Erysipelas*
- Erysipelas is a superficial skin infection, usually caused by *Streptococcus pyogenes*, presenting as a **well-demarcated, intensely erythematous, warm, and painful rash** with a raised border.
- This is an **acute bacterial infection** and would typically be accompanied by systemic symptoms like fever and chills, which are not mentioned in the child's presentation.
Immunology and Allergies Indian Medical PG Question 3: All of the following statements are TRUE about second generation antihistaminic agents EXCEPT:
- A. These may possess additional antiallergic mechanisms
- B. These do not impair psychomotor performance
- C. These lack anticholinergic actions
- D. These possess high anti-motion sickness activity (Correct Answer)
Immunology and Allergies Explanation: ***These possess high anti-motion sickness activity***
- Second-generation antihistamines have **poor penetration** into the central nervous system (CNS), making them ineffective for treating **motion sickness**.
- **First-generation antihistamines**, which readily cross the blood-brain barrier and have **anticholinergic activity**, are typically used for motion sickness.
*These may possess additional antiallergic mechanisms*
- Many second-generation antihistamines, such as **cetirizine** and **loratadine**, have additional anti-inflammatory and **antiallergic properties** beyond H1 receptor blockade.
- These mechanisms can include inhibiting the release of inflammatory mediators and **stabilizing mast cells**.
*These do not impair psychomotor performance*
- Second-generation antihistamines are **non-sedating** because they have limited ability to cross the **blood-brain barrier** and thus do not significantly affect CNS function.
- This characteristic makes them suitable for use without causing **drowsiness** or impairing activities like driving.
*These lack anticholinergic actions*
- Unlike first-generation antihistamines, second-generation agents have **minimal to no affinity** for muscarinic acetylcholine receptors.
- This lack of **anticholinergic activity** means they do not cause side effects such as **dry mouth**, blurred vision, or urinary retention.
Immunology and Allergies Indian Medical PG Question 4: Which immunization is typically given at 6 months of age?
- A. Measles vaccine
- B. DPT vaccine (Correct Answer)
- C. BCG vaccine
- D. None of the options
Immunology and Allergies Explanation: **DPT vaccine**
- The DPT (diphtheria, pertussis, and tetanus) vaccine is administered in multiple doses during infancy as part of the primary immunization series.
- At **6 months of age**, the **third dose of DPT** is typically given (following doses at 6 weeks, 10 weeks, and 14 weeks according to the Indian immunization schedule).
- Among the options provided, DPT is the only vaccine routinely administered at 6 months of age.
- This vaccine protects against three serious bacterial infections: **diphtheria**, which can cause breathing problems; **pertussis (whooping cough)**, a severe respiratory illness; and **tetanus**, which causes painful muscle spasms.
*Measles vaccine*
- The measles vaccine (given as part of the **MMR vaccine** or as MR vaccine in India) is typically administered at **9 to 12 months of age** for the first dose, and a second dose between 15-18 months or 4-6 years.
- It is not routinely given at 6 months, as maternal antibodies can interfere with its effectiveness at this younger age.
*BCG vaccine*
- The BCG (Bacillus Calmette-Guérin) vaccine protects against **tuberculosis** and is given at **birth** or in early infancy as a single dose.
- It is not administered at 6 months of age.
*None of the options*
- This option is incorrect because the **DPT vaccine** (third dose) is a standard immunization given at 6 months of age according to the Indian immunization schedule.
- Multiple vaccines are actually given at 6 months (including OPV, Hepatitis B, Hib, PCV), but among the listed options, only DPT is correct.
Immunology and Allergies Indian Medical PG Question 5: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split.
Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Immunology and Allergies Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1***
**Analysis of Statement 1:**
- A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris**
- The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid
- The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic
- **Statement 1 is CORRECT** ✓
**Analysis of Statement 2:**
- The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris
- This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis
- The intact basal cells standing upright resemble a row of tombstones
- **Statement 2 is CORRECT** ✓
**Does Statement 2 explain Statement 1?**
- Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split
- However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split
- The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis**
- Therefore, **Statement 2 does NOT explain Statement 1** ✗
*Incorrect: Statement 2 is the correct explanation for Statement 1*
- While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism
*Incorrect: Statements 1 and 2 are incorrect*
- Both statements are medically accurate descriptions of Pemphigus vulgaris features
*Incorrect: Statement 1 is incorrect*
- Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
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