Immunopathology Practice Questions

Q: Which type of hypersensitivity is most commonly involved in immediate allergic reactions to penicillin?

Type I. ***Type I*** - Allergic reactions to **penicillin** are primarily mediated by **IgE antibodies** binding to mast cells and basophils [1]. - This binding triggers the release of **histamine** and other inflammatory mediators, leading to symptoms like urticaria, angioedema, and anaphylaxis [2]. *Type II* - This type involves **IgG** or **IgM antibodies** binding to antigens on the surface of host cells, leading to **cell lysis** through complement activation or antibody-dependent cellular cytotoxicity [1]. - While penicillin can rarely cause drug-induced hemolytic anemia (a Type II reaction), the classic allergic reaction is not primarily Type II. *Type III* - Type III hypersensitivity involves the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues, activating complement and causing inflammation [1]. - This is seen in conditions like **serum sickness** or **Arthus reactions**, which are less common with penicillin allergies and involve different mechanisms. *Type IV* - This is a **delayed-type hypersensitivity reaction** mediated by **T lymphocytes** rather than antibodies, typically occurring 24-72 hours after exposure. - Examples include contact dermatitis (e.g., to poison ivy) or the tuberculin skin test, which are distinct from the immediate IgE-mediated response to penicillin. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 211-212.

Q: A 32-year-old woman with a history of recurrent miscarriages and blood clots is diagnosed with antiphospholipid syndrome. What is the most likely underlying cause?

Autoimmune antibodies. ***Autoimmune antibodies*** - Antiphospholipid syndrome is primarily driven by the presence of **autoimmune antibodies**, particularly **anticardiolipin antibodies** and **lupus anticoagulant**. - These antibodies lead to increased risk of **thrombosis** and recurrent miscarriages due to their effects on coagulation pathways. *Genetic mutation* - While certain genetic mutations can predispose individuals to thrombophilia, they do not specifically relate to the **autoimmune nature** seen in antiphospholipid syndrome. - The condition is not predominantly caused by **inherited genetic factors**. *Vitamin K deficiency* - Vitamin K deficiency primarily affects the synthesis of **clotting factors II, VII, IX, and X**, not linked to autoimmune mechanisms. - This condition results in a bleeding tendency rather than **thrombotic events** as seen in antiphospholipid syndrome. *Protein C deficiency* - Protein C deficiency leads to a **hypercoagulable state** but is a distinct genetic thrombophilia not related to the presence of **autoimmune antibodies** [1]. - It does not involve **autoimmune processes** that characterize antiphospholipid syndrome [1].

Q: A patient has recurrent infections and albinism. Examination reveals giant granules in neutrophils. Which genetic disorder is most likely?

Chediak-Higashi syndrome. ***Chediak-Higashi syndrome*** [1] - Characterized by **albinism**, recurrent infections, and the presence of **giant granules** in leukocytes, particularly neutrophils [1]. - Caused by a mutation in the **LYST gene**, leading to defective lysosomal trafficking. *Chronic granulomatous disease* - Primarily associated with **increased susceptibility to catalase-positive organisms**, but does not present with albinism. - Diagnosis is confirmed by the **nitroblue tetrazolium test**, which shows normal granulation in neutrophils. *Wiskott-Aldrich syndrome* - Features include **eczema**, recurrent infections, and **thrombocytopenia**, but lacks the giant granules seen in Chediak-Higashi syndrome. - It involves a mutation in the **WASP gene**, not linked to albinism. *Leukocyte adhesion deficiency* - Presents with recurrent infections due to **impaired leukocyte migration**, but does not feature giant granules or albinism. - The underlying defect is in the **integrins**, which is not associated with the classic findings of Chediak-Higashi syndrome. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 245-246.

Q: Which condition is associated with 'apple-green birefringence' under polarized light when stained with Congo red?

Amyloidosis. ***Amyloidosis*** [1] - Characterized by the deposition of **amyloid proteins** [2], which show **apple-green birefringence** on polarized light when stained with Congo red [1]. - This distinctive finding is crucial for diagnosing **systemic and localized amyloidosis** conditions [1][3]. *Scleroderma* - Involves **collagen deposition** and does not show birefringence characteristic of amyloid when stained with Congo red. - Symptoms include **skin thickening** and **Raynaud's phenomenon**, but lack the signature Congo red staining findings. *Rheumatoid arthritis* - Primarily affects synovial joints and is associated with **rheumatoid factor** and **anti-CCP antibodies**, without any association with amyloid deposits. - The condition primarily involves ***inflammation*** rather than amyloid-related pathology. *Systemic lupus erythematosus* - An autoimmune disorder with a wide range of symptoms but does not exhibit apple-green birefringence in Congo red staining. - Characterized by **antibody production** and multi-organ involvement, but lacks the amyloid deposition 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. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 264-266. [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. 135-136.

Q: Which type of hypersensitivity reaction is mediated by complement?

Type II hypersensitivity. ***Type -2 hypersensitivity*** [1][2] - This type of hypersensitivity involves **IgG or IgM antibodies** binding to antigens on cell surfaces, activating the **complement system**, and mediating cell lysis [1][2]. - It is associated with conditions like **hemolytic anemia** and **Goodpasture syndrome** due to complement activation [1]. *None* - This option suggests there is no complement-mediated hypersensitivity, which contradicts established immunological classifications [2]. - Complement activation is specifically linked to **Type-2 hypersensitivity reactions**, making this option incorrect [1][2]. *Type -4 hypersensitivity* - This is a **T-cell mediated** hypersensitivity, not involving antibodies or complement, making it inappropriate for the question regarding complement-mediated reactions [2]. - Characteristic conditions include **granulomatous diseases** and **contact dermatitis**, distinguishing it from Type-2 hypersensitivity. *Type -1 hypersensitivity* - Type-1 hypersensitivity is primarily **IgE mediated**, involving mast cells and histamine release, without direct involvement of the complement system [2]. - Conditions like **asthma** and **allergic rhinitis** are examples, further separating it from complement-mediated mechanisms [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 214. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210.

Q: The primary defect in chronic granulomatous disease (CGD) is:

Defective H2O2 production. ***Defective H2O2 production*** - Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by the inability of phagocytes (neutrophils, macrophages) to produce **reactive oxygen species**, specifically **superoxide** and its derivatives like H2O2. - This defect is primarily due to mutations in genes encoding components of the **NADPH oxidase enzyme complex**, which is crucial for the **oxidative burst** leading to H2O2 and other antimicrobial agents. *Defective phagocytosis* - Defective phagocytosis refers to an impairment in the engulfment of pathogens, which is not the primary defect in CGD. - In CGD, phagocytes can engulf pathogens, but they cannot effectively kill them intracellularly due to the lack of an **oxidative burst**. *Job's disease* - Job's disease, also known as **hyper-IgE syndrome**, is characterized by high IgE levels, recurrent skin and pulmonary infections, and distinctive facial features. - It is caused by genetic defects in the **STAT3 pathway**, which affects immune cell differentiation and function, and does not involve a primary defect in H2O2 production. *Myeloperoxidase deficiency* - Myeloperoxidase (MPO) deficiency is a condition where neutrophils lack the enzyme **myeloperoxidase**, which contributes to the formation of hypochlorous acid (HOCl) from H2O2 and chloride ions. - While MPO is involved in microbial killing, its deficiency is generally less severe than CGD, as other mechanisms (like H2O2 itself) can still kill pathogens; CGD has a more profound defect in the initial production of ROS.

Q: Which condition is characterized by a Type 4 hypersensitivity reaction?

Temporal arteritis. ***Temporal arteritis*** - This condition is also known as **giant cell arteritis** and is a classic example of a **Type 4 hypersensitivity reaction**, characterized by **T-cell mediated inflammation** of medium to large arteries [1]. - The inflammatory response is driven by activated **T lymphocytes** and **macrophages** infiltrating the arterial walls, leading to giant cell formation and pathology [1]. *Asthma* - **Asthma** is primarily mediated by a **Type 1 hypersensitivity reaction**, involving IgE antibodies and mast cell degranulation upon exposure to allergens. - This leads to immediate release of inflammatory mediators causing **bronchoconstriction** and airway inflammation. *Serum sickness* - **Serum sickness** is a **Type 3 hypersensitivity reaction**, caused by the formation of **immune complexes** (antigen-antibody complexes) that deposit in tissues and trigger inflammation [1]. - These immune complexes activate complement and recruit inflammatory cells, leading to symptoms like fever, rash, and arthralgia [1]. *Myasthenia gravis* - **Myasthenia gravis** is a **Type 2 hypersensitivity reaction**, where circulating **autoantibodies** target and block or destroy acetylcholine receptors at the neuromuscular junction [1]. - This destruction of receptors impairs nerve-to-muscle signaling, causing muscle weakness.

Q: Which of the following is a T-cell mediated disease?

Sarcoidosis. ***Sarcoidosis*** - Sarcoidosis is characterized by the formation of **non-caseating granulomas**, primarily driven by **T-cell accumulation** and activation [1]. - The immune response involves **Th1 lymphocytes** releasing cytokines like **IFN-γ** and **TNF-α**, which promote granuloma formation. *Allergic Rhinitis* - This is a **Type I hypersensitivity reaction** mediated primarily by **IgE antibodies** and **mast cell degranulation**. - While T-cells play a role in orchestrating the IgE response, the immediate symptoms are due to **histamine release**, not direct T-cell cytotoxicity or granuloma formation. *Graves' Disease* - Graves' disease is an **autoimmune disorder** primarily mediated by **autoantibodies** (specifically **thyroid-stimulating immunoglobulins**) that bind to and activate the **TSH receptor**. - Although T-cells are involved in breaking tolerance and supporting B-cell activation, the direct tissue damage and functional changes are antibody-driven. *Systemic Lupus Erythematosus (SLE)* - SLE is a classic **autoimmune disease** characterized by the production of numerous **autoantibodies** (e.g., antinuclear antibodies, anti-dsDNA antibodies) that form **immune complexes**. - These immune complexes deposit in various tissues, leading to inflammation and damage, making it primarily a **Type III hypersensitivity** reaction, heavily B-cell and antibody-mediated. **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. 198-200.

Question 1

Which type of hypersensitivity is most commonly involved in immediate allergic reactions to penicillin?

Accepted Answer

Type I

Answer

Type II

Answer

Type III

Answer

Type IV

Question 2

In a patient with a history of organ transplantation, which type of hypersensitivity reaction is primarily responsible for graft rejection that occurs days to weeks after transplantation?

Accepted Answer

Type IV hypersensitivity

Answer

Type I hypersensitivity

Answer

Type II hypersensitivity

Answer

Type III hypersensitivity

Question 3

A 28-year-old female presents with a rash after using a new cosmetic product. A skin biopsy reveals lymphocytic infiltration around the blood vessels and basal cell vacuolization. Which type of hypersensitivity reaction is most likely involved?

Accepted Answer

Type IV

Answer

Type I

Answer

Type II

Answer

Type III

Question 4

A 32-year-old woman with a history of recurrent miscarriages and blood clots is diagnosed with antiphospholipid syndrome. What is the most likely underlying cause?

Accepted Answer

Autoimmune antibodies

Answer

Genetic mutation

Answer

Vitamin K deficiency

Answer

Protein C deficiency

Question 5

A patient has recurrent infections and albinism. Examination reveals giant granules in neutrophils. Which genetic disorder is most likely?

Accepted Answer

Chediak-Higashi syndrome

Answer

Chronic granulomatous disease

Answer

Leukocyte adhesion deficiency

Answer

Wiskott-Aldrich syndrome

Question 6

Which condition is associated with 'apple-green birefringence' under polarized light when stained with Congo red?

Accepted Answer

Amyloidosis

Answer

Rheumatoid arthritis

Answer

Systemic lupus erythematosus

Answer

Scleroderma

Question 7

Which type of hypersensitivity reaction is mediated by complement?

Accepted Answer

Type II hypersensitivity

Answer

Type I hypersensitivity

Answer

No hypersensitivity reaction

Answer

Type IV hypersensitivity

Question 8

The primary defect in chronic granulomatous disease (CGD) is:

Accepted Answer

Defective H2O2 production

Answer

Job's disease

Answer

Defective phagocytosis

Answer

Myeloperoxidase deficiency

Question 9

Which condition is characterized by a Type 4 hypersensitivity reaction?

Accepted Answer

Temporal arteritis

Answer

Asthma

Answer

Serum sickness

Answer

Myasthenia gravis

Question 10

Which of the following is a T-cell mediated disease?

Accepted Answer

Sarcoidosis

Answer

Allergic Rhinitis

Answer

Graves' Disease

Answer

Systemic Lupus Erythematosus (SLE)

Immunopathology — MCQs

Immunopathology — MCQs

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