Immunology and Allergies

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

Immunology and Allergies Indian Medical PG Question 6: Congenital passive immunity is INADEQUATE in -

• A. Measles
• B. Mumps
• C. RSV (Respiratory Syncytial Virus)
• D. Pertussis (Correct Answer)

Immunology and Allergies Explanation: ***Pertussis*** - **Congenital passive immunity** against *Bordetella pertussis* is **most inadequate** among the listed infections. - **Minimal transplacental transfer** of protective IgG antibodies occurs, and maternal antibodies decline rapidly in infants. - Newborns have **virtually no protection** from maternal antibodies, making them highly susceptible to severe whooping cough. - This is why **early vaccination at 6 weeks** is critical, unlike measles which can wait until 9-12 months. *Measles* - Maternal antibodies provide **excellent passive immunity** protecting infants for **6-9 months**. - This robust protection is why measles vaccination is delayed until 9-12 months of age. - Represents the **gold standard** of effective maternal antibody transfer. *Mumps* - Maternal antibodies provide **good passive immunity** in early infancy. - Mumps in young infants is rare due to this maternal protection. *RSV (Respiratory Syncytial Virus)* - Maternal antibodies provide **limited but present** passive immunity. - Unlike pertussis where protection is nearly absent, RSV maternal antibodies can **reduce severity** of illness. - However, RSV remains a major cause of bronchiolitis in infants despite this partial protection. - The key difference: RSV has **some** maternal protection (inadequate but present), whereas pertussis has **almost none** (most inadequate).

Immunology and Allergies Indian Medical PG Question 7: Neo-natal infection in a Hepatitis 'B' positive pregnant woman can be prevented by administering:

• A. Hepatitis 'B' vaccine
• B. Immunoglobulin
• C. Vaccine and Immunoglobulin (Correct Answer)
• D. Corticosteroids

Immunology and Allergies Explanation: ***Vaccine and Immunoglobulin*** - Administering both the **Hepatitis B vaccine** and **Hepatitis B immune globulin (HBIG)** provides both active and passive immunity to the newborn. - This combination is crucial for preventing perinatal transmission of HBV from an infected mother, significantly reducing the risk of the baby becoming a chronic carrier. *Hepatitis 'B' vaccine* - The vaccine alone provides **active immunity**, which takes time to develop, thus not offering immediate protection against acute exposure at birth. - While essential for long-term protection, it's insufficient as a sole measure for newborns at high risk of immediate infection. *Immunoglobulin* - **Hepatitis B immune globulin (HBIG)** provides **passive immunity**, offering immediate but short-term protection. - It contains pre-formed antibodies that neutralize the virus, but it does not confer lasting immunity. *Corticosteroids* - **Corticosteroids** are used as anti-inflammatory or immunosuppressive agents and have no role in preventing viral infections like Hepatitis B. - Their use in this context would be inappropriate and could even be harmful.

Immunology and Allergies Indian Medical PG Question 8: Hepatitis B vaccine administered at birth is

• A. A pentavalent vaccine
• B. A fixed combination vaccine of Hepatitis B and Hib
• C. A monovalent vaccine of Hepatitis B (Correct Answer)
• D. A combined vaccine of inactivated Polio and Hepatitis B

Immunology and Allergies Explanation: ***A monovalent vaccine of Hepatitis B*** - The **initial dose** of the Hepatitis B vaccine given at birth is a **single-antigen (monovalent)** preparation. It is given as a **standalone vaccine** to ensure prompt protection against Hepatitis B virus. - This early administration is critical for preventing **perinatal transmission** of Hepatitis B from an infected mother to her newborn, and establishing immunity as soon as possible. *A pentavalent vaccine* - **Pentavalent vaccines** typically protect against five different diseases: **Diphtheria, Tetanus, Pertussis (DTP), *Haemophilus influenzae* type b (Hib), and Hepatitis B**. - While Hepatitis B is one component, the vaccine administered at birth is usually monovalent, and the pentavalent vaccine is given later in the infant's immunization schedule. *A fixed combination vaccine of Hepatitis B and Hib* - A fixed combination vaccine of Hepatitis B and **Hib (Haemophilus influenzae type b)** is available and used in some immunization schedules. - However, the **first dose** given at birth is specifically a monovalent Hepatitis B vaccine, not a combined Hib vaccine, to target immediate Hepatitis B protection. *A combined vaccine of inactivated Polio and Hepatitis B* - Combined vaccines that include **inactivated Polio vaccine (IPV)** and **Hepatitis B** do exist but are generally administered later, at 6 weeks and subsequent doses. - The **birth dose** of Hepatitis B vaccine is exclusively for Hepatitis B protection and does not typically include polio antigen.

Immunology and Allergies Indian Medical PG Question 9: Best method to diagnose HIV in an infant?

• A. ELISA
• B. PCR (Correct Answer)
• C. Western blot
• D. All of the options

Immunology and Allergies Explanation: ***PCR*** - **Polymerase Chain Reaction (PCR)** detects **HIV nucleic acids** (DNA or RNA) directly, which is crucial for infants because maternal antibodies can persist for up to 18 months, interfering with antibody-based tests. - PCR allows for early diagnosis, often within the first few weeks or months of life, facilitating timely intervention. *ELISA* - **Enzyme-linked immunosorbent assay (ELISA)** detects HIV antibodies. - In infants, ELISA can be misleading due to the presence of **maternal HIV antibodies** transferred across the placenta, making it unreliable for diagnosing active infection. *Western blot* - **Western blot** is used to confirm positive ELISA results in adults by detecting specific HIV proteins. - Like ELISA, it relies on the detection of **antibodies** and is therefore not reliable in infants due to maternally transmitted antibodies. *All of the options* - This option is incorrect because **ELISA** and **Western blot** are antibody-based tests that are unreliable in infants due to the presence of **maternal antibodies**. - Only **PCR** directly detects the virus itself, making it the preferred diagnostic method in this age group.

Immunology and Allergies Indian Medical PG Question 10: A child presented with perianal itching. The swab specimen is shown in the image. What is the diagnosis?

• A. Enterobius (Correct Answer)
• B. Ascaris
• C. Trichiura
• D. Ancylostoma

Immunology and Allergies Explanation: ***Enterobius*** - The image shows **D-shaped** (plano-convex) and **transparent eggs**, which are characteristic of *Enterobius vermicularis* (**pinworm** or **threadworm**). - **Perianal itching**, especially at night, is the hallmark symptom due to the female worm migrating to the perianal region to lay eggs. *Ascaris* - *Ascaris lumbricoides* eggs are typically **round to oval**, with a thick, mamillated (bumpy) outer shell, or smooth in the case of decorticated eggs, which is different from the eggs pictured. - Infection with *Ascaris* can cause pulmonary symptoms (Loeffler's syndrome) and intestinal obstruction, but not typically perianal itching. *Trichiura* - *Trichuris trichiura* (**whipworm**) eggs are distinctly **barrel-shaped** with prominent **polar plugs** at each end, which is not seen in the image. - Whipworm infection is often associated with bloody diarrhea, rectal prolapse, and growth retardation, not primarily perianal itching. *Ancylostoma* - *Ancylostoma duodenale* and *Necator americanus* (hookworms) eggs are typically **oval** with a **thin shell** and segmented embryo (morula stage) within, which lacks the distinct D-shape and transparency of the pictured eggs. - Hookworm infection primarily causes iron-deficiency anemia and can lead to cutaneous larva migrans, not perianal itching as a primary symptom.

Immunology and Allergies Flashcard 1 of 8

Question: Patients of Reye's syndrome who have recieved IVIG should not recieve live attenuated vaccine for _____ months after IVIG administration

Answer: 11

Immunology and Allergies Flashcard 2 of 8

Question: The symptoms of Job syndrome may be remembered with the mnemonic _____F: coarse FaciesA: cold (noninflamed) staphylococcal Abscesses T: retained primary TeethE: increased IgE D: Dermatologic problems (eczema)

Answer: "FATED":

Immunology and Allergies Flashcard 3 of 8

Question: _____ syndrome is an X-linked recessive disease characterized by triad of thrombocytopenia, eczema and recurrent infections.

Answer: Wiskott Aldrich

Immunology and Allergies Flashcard 4 of 8

Question: The symptoms of Wiskott-Aldrich syndrome may be remembered with the mnemonic "WATER": W: Wiskott A: Aldrich T: _____ E: Eczema R: Recurrent (pyogenic) infections

Answer: Thrombocytopenia (fewer and smaller platelets)

Immunology and Allergies Flashcard 5 of 8

Question: Which laboratory test is diagnostic of juvenile idiopathic arthritis?_____

Answer: None

Immunology and Allergies Flashcard 6 of 8

Question: measles vaccine is given after _____ of gap after giving Ig

Answer: 2-3 months

Extra Information: 

Immunology and Allergies Flashcard 7 of 8

Question: _____-positive oligoarthritis is a subtype of JIA associated with the highest risk for uveitis.

Answer: ANA

Immunology and Allergies Flashcard 8 of 8

Question: Uveitis in juvenile idiopathic arthritis is usually _____terior, non-granulomatous and bilateral.

Answer: an