Immunopathology Practice Questions

Q: Antihistone antibodies are detectable in which of the following conditions?

Drug-induced lupus erythematosus. **Explanation:** **Antihistone antibodies** are the hallmark serological marker for **Drug-induced Lupus Erythematosus (DILE)**. In this condition, certain drugs (most commonly Hydralazine, Procainamide, and Isoniazid) alter the structure of chromatin, leading to the formation of antibodies against histone proteins. These antibodies are present in over **95% of DILE cases**, making them highly sensitive for the diagnosis. Unlike systemic lupus erythematosus (SLE), DILE rarely involves the kidneys or central nervous system and typically resolves upon discontinuation of the offending drug. **Analysis of Incorrect Options:** * **A. CREST Syndrome:** Characterized by **Anti-centromere antibodies** [1]. It is a localized form of systemic sclerosis (Calcinosis, Raynaud’s, Esophageal dysmotility, Sclerodactyly, Telangiectasia). * **B. Polyarteritis Nodosa (PAN):** A systemic necrotizing vasculitis of medium-sized arteries. It is classically **ANCA-negative** and strongly associated with Hepatitis B infection. * **D. Intestinal Lymphoma:** Associated with Celiac disease (Enteropathy-associated T-cell lymphoma) or chronic infections (IPSID), but not with antihistone antibodies. **High-Yield Clinical Pearls for NEET-PG:** 1. **Drug-Induced Lupus:** Most common drugs are **H**ydralazine, **I**soniazid, **P**rocainamide (**HIP**). 2. **SLE vs. DILE:** While antihistone antibodies are seen in both, the absence of **Anti-dsDNA** and **Anti-Sm** antibodies strongly favors a diagnosis of DILE. 3. **Screening Test:** ANA (Antinuclear Antibody) is positive in both SLE and DILE, usually showing a **homogeneous/diffuse** pattern [1]. 4. **Diffuse Systemic Sclerosis:** Associated with **Anti-Scl-70** (Anti-topoisomerase I) antibodies. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 228.

Q: A skin graft was performed on an immunocompromised patient using tissue from another immunocompromised individual. Weeks later, the patient developed contractures and systemic symptoms. What is the most likely cause?

Graft-versus-host disease. ***Correct: Graft-versus-host disease (GVHD)*** - GVHD occurs when **immunocompetent donor T lymphocytes** from the graft recognize recipient tissues as foreign and mount an immune attack [1] - Key scenario: **Immunocompromised recipient** receiving tissue from another person (even if donor is immunocompromised, donor T cells in the graft can still be functional) - The recipient's compromised immune system **cannot eliminate donor lymphocytes**, allowing them to engraft and attack host tissues [1] - **Contractures** are characteristic of chronic GVHD affecting skin and connective tissue - **Systemic symptoms** (fever, diarrhea, hepatitis) reflect multi-organ involvement typical of GVHD - Timeline of **weeks** fits both acute (2-100 days) and chronic (>100 days) GVHD *Incorrect: Delayed wound healing* - Would present as local wound complications, not systemic symptoms - Does not explain contractures or multi-organ involvement - Typically occurs within days, not weeks *Incorrect: Rejection due to recipient T8 cells* - This describes **host-versus-graft** (rejection), not graft-versus-host - Patient is **immunocompromised**, so recipient T cells are impaired and unlikely to mount effective rejection - Would cause graft loss, not systemic symptoms in the recipient *Incorrect: Graft failure* - Non-specific term that doesn't explain the clinical presentation - Would present as loss of graft function/wound dehiscence, not systemic symptoms - Does not account for contractures or multi-organ disease **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 244-245.

Q: A 9-month-old child was admitted to ICU with a history of recurrent sinusitis and otitis media by Staphylococcus aureus. Blood test shows decreased serum IgA, IgG, IgM, IgE, and plasma B cells. What is the diagnosis?

Bruton syndrome. ***Bruton syndrome***- This diagnosis (X-linked agammaglobulinemia or XLA) is defined by the failure of **B cell maturation** due to a mutation in the **BTK gene**, leading to near-total absence of mature B cells and plasma cells.- The clinical presentation is recurrent infections, often *S. aureus* and encapsulated bacteria, correlated with the drastic reduction of all serum **immunoglobulin levels** (IgA, IgG, IgM, IgE).*Ataxia telangiectasia*- This is an **autosomal recessive** T-cell/B-cell defect associated with defects in **DNA repair** (ATM gene), causing progressive cerebellar ataxia and oculocutaneous telangiectasias.- While associated with immunodeficiency, it typically presents with low **IgA** and **IgE**, not the complete absence of plasma B cells seen here.*Chronic granulomatous disease*- This is a phagocytic disorder due to a defect in the **NADPH oxidase** complex, preventing neutrophils from generating a respiratory burst necessary to kill catalase-positive organisms (like *S. aureus*).- Although the child has *S. aureus* infection, **serum Ig and B cell levels** remain normal, which contradicts the profound pan-hypogammaglobulinemia seen in this scenario.*DiGeorge syndrome*- Caused by defective development of the 3rd and 4th pharyngeal pouches, resulting in **T-cell deficiency** (thymic hypoplasia), **hypocalcemia**, and cardiac defects.- The primary immunodeficiency affects T cells, leading to susceptibility to **viral and fungal infections**; B cell numbers are usually normal, even though antibody production might be secondarily impaired.

Q: A young person with recurrent seasonal conjunctivitis presents with itchiness and eye-watering. What is the most likely cell involved in the immediate phase of this condition?

Mast cells. ***Mast cells*** - Seasonal allergic conjunctivitis is a classic Type I **hypersensitivity** reaction (IgE-mediated). The immediate phase is mediated by the degranulation of **mast cells** resident in the conjunctiva. - Upon allergen exposure, cross-linking of surface-bound IgE causes mast cells to release potent preformed mediators, notably **histamine**, which directly causes the immediate onset of **pruritus** (itchiness) and vascular leakage (watering).*Eosinophils* - Eosinophils are primarily associated with the **late-phase** allergic response, recruited to the site hours after the initial reaction. - They contribute to chronic inflammation and tissue damage by releasing major basic protein and other toxic mediators.*Neutrophils* - Neutrophils are the hallmark of **acute inflammation** and are typically abundant in **bacterial infections**, which is not the primary mechanism of this seasonal condition. - While present in some inflammatory states, they are not the primary effector cell governing the immediate symptoms of Type I hypersensitivity.*Lymphocyte* - Lymphocytes, particularly T helper type 2 (Th2) cells, are crucial for promoting the B cell synthesis of **IgE** (sensitization phase). - They drive the overall adaptive immune response but do not mediate the rapid, immediate release of mediators responsible for the acute symptoms.

Question 1

All the following malignancies are associated with HIV, except?

Accepted Answer

Astrocytoma

Answer

Kaposi's Sarcoma

Answer

Non-Hodgkin's lymphoma

Answer

Gastric adenocarcinoma

Question 2

Antihistone antibodies are detectable in which of the following conditions?

Accepted Answer

Drug-induced lupus erythematosus

Answer

CREST syndrome

Answer

Polyarteritis nodosa

Answer

Intestinal lymphoma

Question 3

Which of the following is an example of Type IV hypersensitivity?

Accepted Answer

Granulomatous reaction

Answer

Serum sickness

Answer

Shwartzman reaction

Answer

Arthus reaction

Question 4

MHC restriction is a part of all except:

Accepted Answer

Autoimmune disorder

Answer

Antiviral cytotoxic T cell

Answer

Antibacterial helper T cell/cytotoxic cells

Answer

Allograft rejection

Question 5

A 10-year-old boy is brought to the ED after being stung by a bee while playing outside. Within minutes of the sting, he developed shock, respiratory failure, and vascular collapse. What type of hypersensitivity reaction is most likely responsible?

Accepted Answer

A. IgE-mediated reaction

Answer

D. T cell-mediated response

Answer

B. IgG-mediated reaction

Answer

C. IgA-mediated hypersensitivity

Question 6

Acute hemolytic blood transfusion reactions are mediated by which type of hypersensitivity reaction?

Accepted Answer

Type II

Answer

Type I

Answer

Type III

Answer

Type IV

Question 7

A skin graft was performed on an immunocompromised patient using tissue from another immunocompromised individual. Weeks later, the patient developed contractures and systemic symptoms. What is the most likely cause?

Accepted Answer

Graft-versus-host disease

Answer

Delayed wound healing

Answer

Rejection due to recipient T8 cells

Answer

Graft failure

Question 8

A 9-month-old child was admitted to ICU with a history of recurrent sinusitis and otitis media by Staphylococcus aureus. Blood test shows decreased serum IgA, IgG, IgM, IgE, and plasma B cells. What is the diagnosis?

Accepted Answer

Bruton syndrome

Answer

Chronic granulomatous disease

Answer

DiGeorge syndrome

Answer

Ataxia telangiectasia

Question 9

A young person with recurrent seasonal conjunctivitis presents with itchiness and eye-watering. What is the most likely cell involved in the immediate phase of this condition?

Accepted Answer

Mast cells

Answer

Eosinophils

Answer

Neutrophils

Answer

Lymphocyte

Question 10

Transplant rejection does not occur in which of the following conditions?

Accepted Answer

Severe Combined Immunodeficiency (SCID)

Answer

Bare lymphocyte syndrome

Answer

Chronic granulomatous disease

Answer

DiGeorge syndrome

Immunopathology — MCQs

Immunopathology — MCQs

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