Immunopathology Practice Questions

Q: Which of the following is not found in DiGeorge's syndrome?

Eczema. ***Eczema*** - **Eczema** is NOT a recognized feature of **DiGeorge syndrome** (22q11.2 deletion syndrome). - While individuals with immunodeficiencies may experience various skin conditions, eczema is specifically associated with conditions like **Hyper-IgE syndrome, Wiskott-Aldrich syndrome**, or atopic disorders, not DiGeorge's. - DiGeorge's follows the **CATCH-22 mnemonic**: Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcemia, 22q11 deletion. *Tetany* - **Tetany IS found** in DiGeorge's syndrome due to **hypocalcemia** from parathyroid gland hypoplasia or aplasia. - The lack of parathyroid hormone leads to **low serum calcium levels**, resulting in increased neuromuscular excitability and tetany. *T cell lymphopenia* - **T-cell lymphopenia IS found** in DiGeorge's syndrome due to **thymic hypoplasia or aplasia**. - The primary immunological defect is **T-cell deficiency**, leading to increased susceptibility to viral, fungal, and intracellular bacterial infections. - B-cell numbers are typically normal, though antibody responses may be impaired due to lack of T-cell help. *Mucocutaneous candidiasis* - **This IS found** in patients with DiGeorge's syndrome as an opportunistic infection due to **T-cell immunodeficiency**. - The impaired **cellular immunity** makes individuals highly susceptible to fungal infections like *Candida albicans* affecting mucous membranes and skin.

Q: Acute allergic reaction to the penicillin group of drugs is classified as:

Type 1 reaction. ***Type 1 reaction*** - Penicillin allergy is a classic example of a **Type I hypersensitivity reaction**, mediated by **IgE antibodies**. - Symptoms like **anaphylaxis**, **urticaria**, and **angioedema** develop rapidly upon re-exposure to the drug. *Type 2 reaction* - **Type II hypersensitivity reactions** involve **IgG** or **IgM antibodies** binding to antigens on cell surfaces, leading to cell destruction. - Examples include **hemolytic anemia** due to drug-induced antibodies, which is not the primary mechanism of typical penicillin allergy. *Type 3 reaction* - **Type III hypersensitivity reactions** involve the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues. - This can lead to conditions like **serum sickness** or **vasculitis**, which are less common manifestations of penicillin allergy. *Type 4 reaction* - **Type IV hypersensitivity reactions** are **delayed-type hypersensitivity (DTH)** reactions, mediated by **T cells** rather than antibodies. - These reactions typically manifest 24-72 hours after exposure, as seen in **contact dermatitis**; while some penicillin reactions can be T-cell mediated, the acute, life-threatening allergic response is Type I.

Q: Amyloidosis is associated with the following conditions, except:

Thymoma. ***Thymoma*** - Thymoma is not commonly associated with **systemic deposition of amyloid**. It mainly presents with symptoms related to thymic tumor effects. - This condition primarily arises in **myasthenia gravis** but does not lead to amyloidosis. *Multiple myeloma* - This condition is frequently associated with **AL amyloidosis** due to light chain production [1][2]. - Patients often present with **renal failure** and **proteinuria** along with associated symptoms. *Hypernephroma* - Also known as renal cell carcinoma, it can lead to amyloidosis due to **paraneoplastic syndromes**. - The renal effects are often related to the tumor burden rather than direct amyloid deposition. *Lymphoma* - Similar to multiple myeloma, lymphoma can cause **AL amyloidosis** through increased production of light chains. - Patients may experience systemic symptoms like **weight loss** and **night sweats**, along with evidence of amyloid involvement. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 266-267. [2] 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. 135-136.

Q: What is the special stain that is most diagnostic for amyloidosis?

Congo red with birefringence under polarized light. ***Congo red polarized light*** [1] - This special stain shows **apple-green birefringence** under polarized light [1], which is highly specific for amyloid deposits. - Its ability to bind preferentially to amyloid fibrils makes it the **most diagnostic stain** in confirming the presence of amyloidosis [1]. *Congo red in Illumination* - While Congo red assists in the identification of amyloid, **non-polarized illumination** does not reveal the characteristic birefringence necessary for diagnosis. - It is less definitive as it does not emphasize the **structural features** of amyloid compared to polarized light. *Lugol's Iodine* - Primarily a stain for **glycogen** and other polysaccharides, Lugol's Iodine is not specific to amyloid detection. - It lacks diagnostic utility for amyloidosis, as it does not react with amyloid fibrils in tissue samples. *Sudan black* - Sudan black is used to stain **lipids** and does not interact with amyloid deposits, thus making it unsuitable for amyloid diagnosis. - The stain is effective for identifying **lipid accumulation**, not protein misfolding as seen in amyloidosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

Q: What is the consequence of preformed antibodies in organ transplantation?

Immediate graft failure due to preformed antibodies. ***Hyperacute rejection*** - This occurs immediately after transplant due to **preformed antibodies** reacting against donor antigens, leading to rapid allograft failure [1]. - It is typically associated with **complement activation** and often results in thrombosis of the graft vessels [1]. *Acute rejection* - Primarily mediated by **T cells** rather than preformed antibodies, occurring days to months after transplantation [2]. - Involves a **cellular immune response**, unlike hyperacute rejection which is antibody-mediated [2]. *Acute humoral rejection* - Also involves antibodies but develops **days to weeks** post-transplant rather than immediately like hyperacute rejection. - This type is characterized by a **specific antibody response** and complement activation, but is not due to preformed antibodies. *Chronic rejection* - A long-term process that develops over months to years due to **persistent immune-mediated injury** to the graft, leading to gradual loss of function. - Involves mechanisms such as **tissue fibrosis and vascular changes**, differing from the immediate action of preformed antibodies in hyperacute rejection. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 241-242. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 242.

Q: Which of the following tests would be most beneficial in the diagnosis of a patient suspected of having chronic granulomatous disease of childhood?

Nitroblue tetrazolium (NBT) test. ***Nitroblue tetrazolium (NBT) test*** - The **NBT test** is the **specific diagnostic test** for **chronic granulomatous disease (CGD)** as it directly assesses the defective pathophysiology. - CGD results from defective **NADPH oxidase**, preventing phagocytes from producing a **respiratory burst** needed to kill intracellular pathogens. - In the NBT test, normal phagocytes reduce the yellow NBT dye to blue **formazan** via superoxide production. In CGD, this reaction **fails**, confirming the diagnosis. - This functional assay directly demonstrates the **oxidative burst defect** characteristic of CGD. *E rosette - forming assay* - This assay identifies **T lymphocytes** by their ability to bind sheep red blood cells. - It evaluates **cellular immunity** and T cell numbers, not phagocyte function. - CGD is a **phagocytic disorder**, not a T cell deficiency, making this test irrelevant for diagnosis. *Cell-mediated cytolysis* - This test measures the killing ability of **cytotoxic T lymphocytes (CTLs)** and **NK cells** against target cells. - It assesses **adaptive and innate cellular immunity** but does not evaluate the **phagocytic oxidative burst** that is defective in CGD. *Determination of CD4: CD8 ratio* - This ratio evaluates the balance between **helper (CD4+)** and **cytotoxic (CD8+)** T cell subsets. - It is useful for diagnosing **HIV infection, autoimmune diseases**, and monitoring immunosuppression. - It does not assess **phagocyte function** and is not relevant to the diagnosis of CGD.

Q: Which of the following HLA types is most commonly associated with rheumatoid arthritis?

HLA DR4. ***Correct: HLA DR4*** - **HLA-DR4** is the **most strongly associated HLA type with rheumatoid arthritis** globally and is found in a majority of affected individuals. - This association is primarily with the **"shared epitope" alleles within the HLA-DRB1 locus** (particularly HLA-DRB1*04), contributing to genetic susceptibility and disease severity. - The shared epitope hypothesis explains how specific amino acid sequences in the HLA-DR beta chain increase RA risk. *Incorrect: HLA DR8* - While other HLA-DR types may show minor associations in certain populations or with specific disease manifestations, **DR8 is not the primary or most common association** for rheumatoid arthritis. - Its association, if any, is **significantly weaker** compared to HLA-DR4. *Incorrect: HLA DQ1* - **HLA-DQ1** (also known as HLA-DQB1*05 and DQB1*06) is a class II MHC molecule, but it is **not the primary HLA type associated with rheumatoid arthritis**. - While HLA-DQ genes can contribute to autoimmune disease susceptibility, **HLA-DRB1 alleles, particularly DR4**, have a stronger and more consistent link to RA. *Incorrect: HLA B27* - **HLA-B27** is a well-known genetic marker, but it is **classically associated with seronegative spondyloarthropathies** like ankylosing spondylitis, psoriatic arthritis, and reactive arthritis—**not rheumatoid arthritis**. - Its presence is a strong indicator for conditions characterized by **axial skeletal involvement and enthesitis**, differentiating them from RA, which primarily affects peripheral joints symmetrically.

Question 1

Which of the following is not found in DiGeorge's syndrome?

Accepted Answer

Eczema

Answer

Tetany

Answer

T cell lymphopenia

Answer

Mucocutaneous candidiasis

Question 2

Which of the following statements about transplant rejection reactions is false:

Accepted Answer

Liver is extremely sensitive to hyperacute rejection

Answer

Acute rejection is readily reversible with appropriate treatment

Answer

Hyperacute rejection is uncommon

Answer

Chronic rejection is a major cause of late graft loss

Question 3

Acute allergic reaction to the penicillin group of drugs is classified as:

Accepted Answer

Type 1 reaction

Answer

Type 2 reaction

Answer

Type 3 reaction

Answer

Type 4 reaction

Question 4

Amyloidosis is associated with the following conditions, except:

Accepted Answer

Thymoma

Answer

Multiple myeloma

Answer

Lymphoma

Answer

Hypernephroma

Question 5

Type I hypersensitivity includes all of the following except:

Accepted Answer

Autoimmune hemolytic anemia

Answer

Extrinsic asthma

Answer

Hay fever

Answer

Anaphylaxis

Question 6

Which of the following histologic alterations is most characteristic of Sjögren's syndrome?

Accepted Answer

Intense lymphocytic infiltration of the gland replacing the acinar structures.

Answer

Proliferation of the ductal epithelium.

Answer

Atrophy of the glands due to lymphocytic infiltration.

Answer

All of the options.

Question 7

What is the special stain that is most diagnostic for amyloidosis?

Accepted Answer

Congo red with birefringence under polarized light

Answer

Lugol’s Iodine

Answer

Sudan black

Answer

Congo red without birefringence under polarized light

Question 8

What is the consequence of preformed antibodies in organ transplantation?

Accepted Answer

Immediate graft failure due to preformed antibodies

Answer

Delayed T-cell mediated rejection

Answer

Long-term graft dysfunction due to chronic inflammation

Answer

Post-transplant antibody-mediated rejection

Question 9

Which of the following tests would be most beneficial in the diagnosis of a patient suspected of having chronic granulomatous disease of childhood?

Accepted Answer

Nitroblue tetrazolium (NBT) test

Answer

E rosette - forming assay

Answer

Cell-mediated cytolysis

Answer

Determination of CD4: CD8 ratio

Question 10

Which of the following HLA types is most commonly associated with rheumatoid arthritis?

Accepted Answer

HLA DR4

Answer

HLA DR8

Answer

HLA DQ1

Answer

HLA B27

Immunopathology — MCQs

Immunopathology — MCQs

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