Immunopathology Practice Questions

Q: Thymoma may be associated with all the following conditions, EXCEPT:

Crohn's disease. **Explanation:** Thymomas are epithelial neoplasms of the thymus that are uniquely associated with a wide spectrum of **paraneoplastic autoimmune syndromes**. This association occurs because the neoplastic thymus fails to properly "educate" T-cells (defective negative selection), leading to the escape of self-reactive T-lymphocytes into the systemic circulation. **Why Crohn’s Disease is the Correct Answer:** While thymomas are linked to various autoimmune conditions, **Crohn’s disease** is notably **not** associated with thymoma. In contrast, **Ulcerative Colitis (Option C)** has a documented, albeit rare, association with thymic tumors. This distinction is a classic "except" style question in pathology exams. **Analysis of Incorrect Options:** * **Polymyositis (Option A):** Inflammatory myopathies (including polymyositis and dermatomyositis) are well-recognized paraneoplastic manifestations of thymoma, second only to Myasthenia Gravis in frequency among muscle-related associations. * **Sjogren’s Syndrome (Option B):** Various connective tissue and rheumatologic diseases, including Sjogren’s syndrome, Systemic Lupus Erythematosus (SLE), and Rheumatoid Arthritis, are associated with thymic epithelial tumors. * **Ulcerative Colitis (Option C):** Inflammatory Bowel Disease, specifically Ulcerative Colitis, is a recognized paraneoplastic association of thymoma, unlike Crohn's disease. **NEET-PG High-Yield Pearls:** 1. **Most Common Association:** **Myasthenia Gravis** (seen in ~30-45% of thymoma patients). 2. **Pure Red Cell Aplasia (PRCA):** A highly specific association; ~50% of PRCA patients have an underlying thymoma. 3. **Hypogammaglobulinemia:** Known as **Good Syndrome** (Thymoma + Hypogammaglobulinemia). 4. **Other Associations:** Graves' disease, Pernicious anemia, and Alopecia areata.

Q: Which defect is identified by the nitroblue tetrazolium test?

Phagocytosis. The **Nitroblue Tetrazolium (NBT) test** is a classic diagnostic tool used to assess the **oxidative burst** capacity of phagocytes (neutrophils and macrophages). Phagocytosis involves the ingestion of pathogens, followed by their destruction via reactive oxygen species (ROS) [1]. This process is mediated by the **NADPH oxidase enzyme complex**. In a normal cell, NADPH oxidase reduces the yellow NBT dye into insoluble, dark blue **formazan crystals**. A positive NBT test (blue color) indicates intact phagocytic killing power. A negative NBT test (no color change) indicates a defect in the oxidative burst, most characteristically seen in **Chronic Granulomatous Disease (CGD)**. Complement defects are typically screened using the **CH50 assay** (for classical pathway) or **AH50** (for alternative pathway). T-cell function is evaluated via delayed-type hypersensitivity (DTH) skin tests, flow cytometry (CD3/CD4/CD8 counts), or mitogen stimulation assays. B-cell function is assessed by measuring serum immunoglobulin levels (IgG, IgA, IgM) or quantifying CD19/CD20+ cells via flow cytometry. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 89-92.

Question 1

SLE is which type of hypersensitivity reaction?

Accepted Answer

Type III hypersensitivity

Answer

Type I hypersensitivity

Answer

Type II hypersensitivity

Answer

Type IV hypersensitivity

Question 2

Which of the following cytokines are anti-inflammatory in nature?

Accepted Answer

All of the above

Answer

IL-4

Answer

IL-10

Answer

TGF-β

Question 3

C-ANCA positivity indicates antibodies formed against which of the following?

Accepted Answer

Proteinase 3

Answer

Myeloperoxidase

Answer

Cytoplasmic antinuclear Antibody

Answer

Anti centromere Antibody

Question 4

Thymoma may be associated with all the following conditions, EXCEPT:

Accepted Answer

Crohn's disease

Answer

Polymyositis

Answer

Sjogren's syndrome

Answer

Ulcerative colitis

Question 5

Which of the following is NOT a type II hypersensitivity reaction?

Accepted Answer

Hemorrhagic disease of the newborn

Answer

Graves disease

Answer

Autoimmune hemolytic anemia

Answer

Acute rheumatic fever

Question 6

Which HLA marker is associated with gluten-sensitive enteropathy?

Accepted Answer

DQ2 and DQ8

Answer

DR3 and DQ1

Answer

DR4

Answer

B27

Question 7

Which defect is identified by the nitroblue tetrazolium test?

Accepted Answer

Phagocytosis

Answer

Complement

Answer

T cell

Answer

B cell

Question 8

Hot agglutinin is found in all conditions except:

Accepted Answer

Mycoplasma infection

Answer

Systemic Lupus Erythematosus (SLE)

Answer

Methyl dopa

Answer

Rheumatoid arthritis

Question 9

Which of the following is an organ-specific autoimmune disease?

Accepted Answer

Goodpasture's syndrome

Answer

Systemic Lupus Erythematosus (SLE)

Answer

Rheumatoid Arthritis (RA)

Answer

Polyarteritis Nodosa (PAN)

Question 10

Which of the following cells is NOT involved in HIV infection?

Accepted Answer

Neutrophils

Answer

Macrophages

Answer

Lymphocytes

Answer

Dendritic cells

Immunopathology — MCQs

Immunopathology — MCQs

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