Immunopathology Practice Questions

Q: A 6-year-old boy presented with recurrent pyogenic abscess, runny nose, oral thrush, and rash on perineal areas. Pus culture showed growth of Staphylococcus aureus. A test was performed whose finding is shown below. What is the most common mode of inheritance of this disorder?

X-linked recessive. ***X-linked recessive*** - The clinical presentation of recurrent **pyogenic abscesses** and **Staphylococcus aureus** infections in a young boy strongly suggests **Chronic Granulomatous Disease (CGD)**, with X-linked inheritance being the most common form (65-70% of cases). - X-linked CGD is caused by mutations in the **gp91phox gene (CYBB)** on the X chromosome, explaining why males are predominantly affected with this severe phenotype. *Autosomal recessive* - While autosomal recessive forms of CGD do exist (accounting for 30-35% of cases), they are **less common** than X-linked inheritance. - Autosomal recessive CGD involves mutations in genes like **p22phox**, **p47phox**, or **p67phox**, but X-linked remains the predominant inheritance pattern. *Autosomal dominant* - CGD does not typically follow an **autosomal dominant** inheritance pattern as it requires complete loss of **NADPH oxidase function**. - Heterozygous carriers usually have sufficient enzyme activity to prevent the severe immunodeficiency seen in this patient. *Mitochondrial inheritance* - **Mitochondrial inheritance** affects both males and females equally and is passed through the maternal line. - CGD specifically involves defects in the **NADPH oxidase complex** located in phagocytic cell membranes, not mitochondrial dysfunction.

Q: Antinuclear antibodies are seen in which of the following conditions?

All of the above. Antinuclear antibodies (ANA) are a group of autoantibodies directed against various components of the cell nucleus (DNA, RNA, histones, and nucleoproteins). While ANA is the hallmark screening test for **Systemic Lupus Erythematosus (SLE)**, it is not specific to it [1]. ANA can be positive in a wide range of systemic autoimmune rheumatic diseases (SARDs), chronic infections, and even in a small percentage of healthy individuals [2]. * **Systemic Lupus Erythematosus (SLE):** ANA is the best initial screening test for SLE due to its extremely high sensitivity (95–99%) [1]. A negative ANA test virtually rules out SLE. * **Rheumatoid Arthritis (RA):** Although Rheumatoid Factor (RF) and Anti-CCP are more specific, approximately 30–50% of RA patients test positive for ANA [2]. * **Sjögren’s Syndrome:** ANA is positive in approximately 70–80% of patients, often associated with specific antibodies like Anti-Ro (SS-A) and Anti-La (SS-B) [2]. Since ANA is prevalent in all three conditions, **"All of the above"** is the correct choice. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for ANA Detection:** Indirect Immunofluorescence (IIF) on HEp-2 cells. * **Specific vs. Sensitive:** ANA is highly **sensitive** for SLE, but **Anti-dsDNA** and **Anti-Smith (Sm)** are highly **specific** [1]. * **Drug-Induced Lupus:** Characterized by **Anti-histone antibodies** (ANA is almost always positive). * **Mixed Connective Tissue Disease (MCTD):** Characterized by high titers of **Anti-U1 RNP** antibodies. * **Scleroderma (Systemic Sclerosis):** **Anti-Scl-70** (Diffuse) and **Anti-centromere** (Limited/CREST) [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 226-227. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 228.

Question 1

TH1 cells are produced by which of the following cell types?

Accepted Answer

Helper T-cells

Answer

Memory T cells

Answer

Cytotoxic T cells

Answer

Suppressor T cells

Question 2

Which CD molecule is important for the presentation of lipid antigens?

Accepted Answer

CD1

Answer

CD4

Answer

CD8

Answer

CD16

Question 3

All are true regarding agammaglobulinemia except:

Accepted Answer

Decreased red pulp in spleen

Answer

Loss of germinal center in lymph node

Answer

Normal cortical lymphocytes

Answer

Normal cortical lymphocytes in paracortex and medulla

Question 4

The Nitroblue tetrazolium test is used to assess the function of which cells?

Accepted Answer

Phagocytes

Answer

Complement

Answer

T cells

Answer

B cells

Question 5

A 6-year-old boy presented with recurrent pyogenic abscess, runny nose, oral thrush, and rash on perineal areas. Pus culture showed growth of Staphylococcus aureus. A test was performed whose finding is shown below. What is the most common mode of inheritance of this disorder?

Accepted Answer

X-linked recessive

Answer

Autosomal recessive

Answer

Autosomal dominant

Answer

Mitochondrial inheritance

Question 6

Which immunoglobulin (Ig) is primarily active in Type 1 hypersensitivity reactions?

Accepted Answer

IgE

Answer

IgA

Answer

IgD

Answer

IgG

Question 7

A 10-year-old boy with a history of recurrent bacterial infections presents with fever and a productive cough. Biochemical analysis of his neutrophils demonstrates defective oxidative burst. This patient most likely has inherited mutations in the gene that encodes which of the following proteins?

Accepted Answer

NADPH oxidase

Answer

Catalase

Answer

Cytochrome P450

Answer

Myeloperoxidase

Question 8

Which is the most important Human Leukocyte Antigen (HLA) locus for organ transplantation and tissue typing?

Accepted Answer

HLA-D

Answer

HLA-A

Answer

HLA-B

Answer

HLA-C

Question 9

Antinuclear antibodies are seen in which of the following conditions?

Accepted Answer

All of the above

Answer

Systemic lupus erythematosus (SLE)

Answer

Rheumatoid arthritis (RA)

Answer

Sjögren's syndrome

Question 10

All of the following autoimmune disorders are more common in females, except:

Accepted Answer

Type I diabetes

Answer

Idiopathic Thrombocytopenic Purpura (ITP)

Answer

Multiple sclerosis

Answer

Scleroderma

Immunopathology — MCQs

Immunopathology — MCQs

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