Immunopathology Practice Questions

Q: Which of the following is an example of a type 3 hypersensitivity reaction?

Serum sickness. **Explanation:** Hypersensitivity reactions are classified based on the underlying immune mechanism. **Type 3 Hypersensitivity** is mediated by **Immune Complexes** (Antigen-Antibody complexes). These complexes circulate in the blood and deposit in tissues (like joints, kidneys, and blood vessels), triggering complement activation and neutrophil recruitment, leading to tissue damage. **Why Serum Sickness is Correct:** Serum sickness is the classic systemic example of Type 3 hypersensitivity. It occurs when foreign proteins (antigens) are injected, leading to the formation of soluble immune complexes that deposit in various organs. Clinical features typically include fever, rash, polyarthritis, and glomerulonephritis. **Analysis of Incorrect Options:** * **Goodpasture Syndrome (Option A):** This is a **Type 2** (Cytotoxic) reaction. It involves antibodies (Anti-GBM) binding directly to fixed antigens on the basement membranes of lungs and kidneys. * **Autoimmune Hemolytic Anemia (Option C):** This is also a **Type 2** reaction. Antibodies bind to antigens on the surface of red blood cells, leading to their destruction via the complement system or phagocytosis. * **Asthma (Option D):** This is a **Type 1** (Immediate) reaction. It is mediated by IgE antibodies causing mast cell degranulation upon exposure to allergens. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Hypersensitivity:** **ACID** (Type 1: **A**naphylactic/Atopic; Type 2: **C**ytotoxic; Type 3: **I**mmune Complex; Type 4: **D**elayed). * **Type 3 Examples:** SLE, Post-Streptococcal Glomerulonephritis (PSGN), Arthus reaction (local), and Rheumatoid Arthritis. * **Key Mediator:** Complement components (C3a, C4a, C5a) are consumed, leading to low serum complement levels during active Type 3 disease.

Q: Type 5 hypersensitivity reaction is a modification of?

Type 2 hypersensitivity reaction. **Explanation:** **Type 5 hypersensitivity** (also known as Stimulatory Hypersensitivity) is considered a modification of **Type 2 hypersensitivity** because both involve antibodies (IgG or IgM) binding directly to antigens on the cell surface. * **Why Type 2 is correct:** In classic Type 2 reactions, antibodies lead to cell destruction (via complement or phagocytosis). In Type 5, the antibodies do not destroy the cell; instead, they bind to cell-surface receptors and **mimic the action of natural ligands**, leading to overstimulation of the cell's function. Because the mechanism involves site-specific antibody-antigen binding, it is classified as a subtype of Type 2. * **Why others are incorrect:** * **Type 1:** Involves IgE-mediated mast cell degranulation (Allergy/Anaphylaxis). * **Type 3:** Involves the deposition of circulating **Antigen-Antibody complexes** in tissues, not direct binding to cell-surface receptors. * **Type 4:** Is a **delayed-type** reaction mediated by T-cells, not antibodies. **Clinical Pearls for NEET-PG:** 1. **Classic Example:** **Graves’ Disease**. Here, Long-Acting Thyroid Stimulators (LATS) / Thyroid Stimulating Immunoglobulins (TSI) bind to TSH receptors, stimulating excess thyroid hormone production. 2. **Another Example:** **Myasthenia Gravis** (though often grouped under Type 2, it involves antibodies blocking/internalizing ACh receptors). 3. **Key Distinction:** If the question asks for the mechanism of Graves' disease and Type 5 is not an option, always choose **Type 2**. 4. **Coombs Classification:** The original Gell and Coombs classification described four types; Type 5 was added later as a specialized variant of Type 2.

Q: What is atopy in the context of hypersensitivity?

Local type I hypersensitivity. **Explanation:** **Atopy** refers to a genetic predisposition to develop localized immediate hypersensitivity reactions to common environmental allergens (such as pollen, house dust mites, or animal dander). **1. Why Option B is Correct:** Atopy is a **Local Type I Hypersensitivity** reaction. It is mediated by **IgE antibodies** bound to mast cells in specific target organs. When an allergen is inhaled, ingested, or touches the skin, it triggers mast cell degranulation in that specific area, leading to localized symptoms. Common clinical manifestations include allergic rhinitis (hay fever), bronchial asthma, and atopic dermatitis (eczema). **2. Why Other Options are Incorrect:** * **Option A:** Systemic Type I hypersensitivity refers to **Anaphylaxis**. Unlike atopy, anaphylaxis is a generalized, life-threatening reaction involving multiple organ systems (e.g., hypotension, laryngeal edema) following systemic exposure to an allergen (e.g., bee sting or IV drugs). * **Options C & D:** Type II hypersensitivity involves **cytotoxic antibodies** (IgG/IgM) directed against cell surface antigens (e.g., Rh incompatibility or Myasthenia Gravis). Atopy is strictly a Type I (IgE-mediated) mechanism. **High-Yield Clinical Pearls for NEET-PG:** * **Genetic Link:** Atopy is often associated with a family history and elevated serum IgE levels. * **The "Atopic March":** This describes the progression from atopic dermatitis in infancy to allergic rhinitis and asthma in later childhood. * **Cytokine Profile:** Atopy is driven by **Th2 cells**, which secrete **IL-4** (induces IgE switching), **IL-5** (activates eosinophils), and **IL-13** (stimulates mucus secretion). * **Diagnosis:** Primarily via the **Skin Prick Test** (Wheal and Flare reaction) or RAST (Radioallergosorbent test).

Q: Which of the following types of hypersensitivity reaction is found in the given condition?

Cytotoxic type. ***Cytotoxic type*** - **Type II hypersensitivity** involves **antibody-mediated** destruction of cells through **complement activation** and **antibody-dependent cellular cytotoxicity (ADCC)**. - Classic examples include **hemolytic disease of newborn**, **autoimmune hemolytic anemia**, and **Goodpasture's syndrome** where antibodies target cell surface antigens. *Anaphylactic type* - **Type I hypersensitivity** is mediated by **IgE antibodies** and **mast cell degranulation** releasing **histamine** and other mediators. - Examples include **anaphylaxis**, **allergic asthma**, and **atopic dermatitis** - immediate reactions occurring within minutes. *Type III hypersensitivity* - **Immune complex-mediated** reactions involving **antigen-antibody complexes** depositing in tissues and activating **complement**. - Examples include **serum sickness**, **systemic lupus erythematosus**, and **post-streptococcal glomerulonephritis** with tissue inflammation. *Cell-mediated hypersensitivity* - **Type IV hypersensitivity** is **T-cell mediated** involving **delayed-type hypersensitivity** with **macrophage activation**. - Examples include **tuberculin skin test**, **contact dermatitis**, and **organ transplant rejection** occurring 24-72 hours after exposure.

Question 1

Which of the following can provide the "second signal" to a B-cell bound by a specific antigen?

Accepted Answer

Antigen-specific T-cells

Answer

Epstein-Barr virus

Answer

Endotoxin

Answer

Plasma cells

Question 2

Which of the following is an example of a type 3 hypersensitivity reaction?

Accepted Answer

Serum sickness

Answer

Goodpasture syndrome

Answer

Autoimmune hemolytic anemia (AHA)

Answer

Asthma

Question 3

All of the following organs are needed for biopsy to prove GVHD except?

Accepted Answer

Liver

Answer

Kidney

Answer

Skin

Answer

Intestine

Question 4

A 55-year-old diabetic patient with a history of renal failure awaiting transplant and undergoing hemodialysis develops amyloid deposits around the joints. What substance are these deposits likely composed of?

Accepted Answer

Beta2 microglobulin

Answer

Amyloid-associated protein

Answer

Amyloid light chains

Answer

Calcitonin precursors

Question 5

Type 5 hypersensitivity reaction is a modification of?

Accepted Answer

Type 2 hypersensitivity reaction

Answer

Type 1 hypersensitivity reaction

Answer

Type 3 hypersensitivity reaction

Answer

Type 4 hypersensitivity reaction

Question 6

What is atopy in the context of hypersensitivity?

Accepted Answer

Local type I hypersensitivity

Answer

Systemic type I hypersensitivity

Answer

Systemic type II hypersensitivity

Answer

Local type II hypersensitivity

Question 7

Which of the following types of hypersensitivity reaction is found in the given condition?

Accepted Answer

Cytotoxic type

Answer

Anaphylactic type

Answer

Type III hypersensitivity

Answer

Cell-mediated hypersensitivity

Question 8

Which of the following is true about Graft-versus-Host Disease (GVHD)?

Accepted Answer

Occurs when donor cells are immunocompetent.

Answer

Occurs when the host is immunocompetent.

Answer

The most common organ involved is the lung.

Answer

It is most common in renal transplants.

Question 9

MHC restriction to antigen presentation is not done for which of the following?

Accepted Answer

Graft rejection

Answer

Killing of viruses by cytotoxic cells

Answer

Killing of bacteria by helper cells

Answer

T cell activation in autoimmunity

Question 10

Which of the following is an example of immune complex-mediated (Type III) hypersensitivity?

Accepted Answer

Systemic lupus erythematosus

Answer

Anaphylaxis

Answer

Autoimmune hemolytic anemia

Answer

Type 1 diabetes

Immunopathology — MCQs

Immunopathology — MCQs

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