Immunopathology Practice Questions

Q: All are true about Bloom syndrome except?

Decreased levels of IgG. **Explanation:** Bloom Syndrome is a rare autosomal recessive disorder caused by a mutation in the **BLM gene**, which encodes a **DNA helicase** enzyme. This defect leads to genomic instability and excessive sister chromatid exchanges. **Why Option A is the "Except" (Correct Answer):** In Bloom Syndrome, there is a generalized state of humoral immunodeficiency. The characteristic finding is a **pan-hypogammaglobulinemia**, meaning there are **decreased levels of all major immunoglobulin classes (IgG, IgA, and IgM)**. Therefore, the statement "Decreased levels of IgG" is actually **true** regarding the disease. Since the question asks for the "Except" (the false statement), and all options A, B, and C describe the typical decrease in immunoglobulins, this question likely contains a technical error in its framing or the provided key. However, in the context of standard medical literature, **Raised IgE levels (Option D)** is the most distinctively **false** statement, as IgE is not typically elevated in this condition. **Analysis of Options:** * **Options A, B, & C:** These are **true** clinical features. Most patients exhibit low serum concentrations of IgG, IgA, and IgM, leading to recurrent sinopulmonary infections. * **Option D:** This is **false**. Unlike Job Syndrome (Hyper-IgE) or Wiskott-Aldrich Syndrome, Bloom Syndrome is not associated with elevated IgE. **Clinical Pearls for NEET-PG:** * **Triad:** Telangiectatic erythema (butterfly distribution on the face), photosensitivity, and severe growth retardation (dwarfism). * **Cytogenetic Hallmark:** Increased **Sister Chromatid Exchange (SCE)** and "quadriradial" configurations in lymphocytes. * **Cancer Risk:** Extremely high predisposition to various malignancies (leukemia, lymphoma, and carcinomas) at a very young age. * **Inheritance:** Autosomal Recessive (BLM gene, Chromosome 15).

Q: A patient presents with a history of episodic painful edema of the face and larynx, associated with abdominal pain, particularly during periods of stress. Which of the following is likely to be deficient?

C1 Esterase Inhibitor. **Explanation:** The clinical presentation of episodic, non-pitting edema of the face, larynx, and gastrointestinal tract (causing abdominal pain) triggered by stress or trauma is classic for **Hereditary Angioedema (HAE)**. **Why C1 Esterase Inhibitor is correct:** HAE is caused by an autosomal dominant deficiency or dysfunction of the **C1 esterase inhibitor (C1-INH)**. C1-INH normally regulates the classical complement pathway and the kinin system. Its deficiency leads to the uncontrolled activation of C1 and the kallikrein-kinin cascade. This results in excessive production of **Bradykinin**, a potent vasodilator that increases vascular permeability [1], leading to the characteristic angioedema. **Why other options are incorrect:** * **Complement C3/C5:** Deficiency of these late-pathway components typically presents with increased susceptibility to pyogenic bacterial infections (C3) or disseminated Neisserial infections (C5-C9). They do not cause angioedema. * **Properdin:** This is a positive regulator of the alternative pathway. Its deficiency is X-linked and predisposes individuals to severe meningococcal disease. **High-Yield NEET-PG Pearls:** * **Diagnosis:** Screening shows **low C4 levels** (even between attacks) because C1-INH cannot stop C1 from consuming C4. C1 levels remain normal. * **Management:** Acute attacks are treated with C1-INH concentrate or **Icatibant** (Bradykinin B2 receptor antagonist). * **Contraindication:** **ACE inhibitors** are strictly contraindicated in these patients as they prevent bradykinin breakdown, potentially triggering a fatal laryngeal edema. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 100-101.

Q: Hemolytic disease of the newborn is which type of hypersensitivity reaction?

Type II. **Explanation:** **Hemolytic Disease of the Newborn (HDN)**, also known as Erythroblastosis Fetalis, is a classic example of **Type II (Cytotoxic) Hypersensitivity**. **Why Type II is correct:** Type II hypersensitivity is mediated by **IgG or IgM antibodies** directed against antigens on specific cell surfaces or tissues. In HDN (specifically Rh incompatibility), maternal anti-D IgG antibodies cross the placenta and bind to Rh antigens on the fetal red blood cell (RBC) membrane. This leads to RBC destruction via two mechanisms: 1. **Opsonization** and subsequent phagocytosis by splenic macrophages. 2. **Complement-mediated lysis.** Since the damage is localized to a specific cell type (RBCs) via antibody binding, it fits the Type II definition. **Why other options are incorrect:** * **Type I (Immediate):** Mediated by **IgE** and mast cell degranulation (e.g., Anaphylaxis, Asthma). * **Type III (Immune-complex):** Involves soluble antigen-antibody complexes depositing in tissues/vessels (e.g., SLE, Post-streptococcal glomerulonephritis). * **Type IV (Delayed):** Cell-mediated reaction involving **T-lymphocytes**, not antibodies (e.g., Mantoux test, Contact dermatitis). **High-Yield Clinical Pearls for NEET-PG:** * **Coombs Test:** The **Direct Coombs Test** is used to detect antibodies already bound to the baby’s RBCs (positive in HDN). The **Indirect Coombs Test** checks for anti-Rh antibodies in the mother's serum. * **Prophylaxis:** Administering **Anti-D (RhoGAM)** to an Rh-negative mother at 28 weeks and within 72 hours of delivery prevents sensitization. * **Other Type II Examples:** Myasthenia Gravis, Goodpasture Syndrome, Rheumatic Fever, and Pemphigus Vulgaris.

Q: Hemolytic disease of the newborn is an example of which type of hypersensitivity reaction?

Type 2 hypersensitivity reaction. **Explanation:** **Hemolytic Disease of the Newborn (HDN)**, also known as Erythroblastosis Fetalis, is a classic example of a **Type 2 Hypersensitivity Reaction**. [5] **Why the correct answer is right:** Type 2 hypersensitivity is **antibody-mediated (cytotoxic)**. It occurs when IgG or IgM antibodies bind to antigens on the surface of specific cells (in this case, fetal Rh+ red blood cells). [2] This binding leads to cell destruction via three mechanisms: 1. **Complement-mediated lysis.** 2. **Opsonization and phagocytosis** by macrophages in the spleen. [1] 3. **Antibody-dependent cellular cytotoxicity (ADCC).** In HDN, maternal anti-Rh IgG antibodies cross the placenta and destroy fetal RBCs, leading to anemia and jaundice. [5] **Why incorrect options are wrong:** * **Type 3 Hypersensitivity:** Involves the deposition of **soluble antigen-antibody (immune) complexes** in tissues (e.g., SLE, Post-streptococcal glomerulonephritis), rather than antibodies attacking cell-surface antigens. * **Arthus Reaction:** This is a localized form of **Type 3 hypersensitivity** characterized by edema and necrosis following an intradermal injection of an antigen in a sensitized individual. * **Type 4 Hypersensitivity:** This is **cell-mediated (delayed)**, involving T-lymphocytes rather than antibodies (e.g., Mantoux test, contact dermatitis). **Clinical Pearls for NEET-PG:** * **Coombs Test:** The **Direct Coombs test** is used to detect antibodies already bound to fetal RBCs, while the **Indirect Coombs test** [3] detects anti-Rh antibodies in maternal serum. * **Prophylaxis:** Administering **Anti-D (Rhophylac/RhoGAM)** to an Rh-negative mother at 28 weeks and within 72 hours of delivery prevents sensitization. * **Other Type 2 Examples:** Myasthenia Gravis, Graves' disease, Goodpasture syndrome, and Rheumatic fever. [4]

Q: Atopy is primarily mediated by which immunoglobulin class?

IgE. **Explanation:** **Atopy** refers to the genetic predisposition to develop localized hypersensitivity reactions to common environmental allergens. This process is the hallmark of **Type I Hypersensitivity** (Immediate Hypersensitivity). 1. **Why IgE is Correct:** In atopic individuals, exposure to an allergen triggers Th2 cells to release cytokines (IL-4, IL-13), which induce B-cells to undergo class switching to produce **IgE**. These IgE antibodies bind to high-affinity **FcεRI receptors** on the surface of **mast cells and basophils** (sensitization). Upon re-exposure, the allergen cross-links the bound IgE, leading to degranulation and the release of vasoactive amines like histamine, causing symptoms of asthma, allergic rhinitis, or eczema. 2. **Why Other Options are Incorrect:** * **IgD:** Primarily acts as a B-cell surface receptor; its secreted function is largely unknown and not involved in allergy. * **IgM:** The first antibody produced in a primary immune response and a potent activator of the classical complement pathway. It is involved in Type II and Type III hypersensitivity, but not atopy. * **IgA:** The primary secretory immunoglobulin found in mucosal surfaces (tears, saliva, colostrum). It provides local mucosal immunity rather than mediating allergic triggers. **High-Yield Clinical Pearls for NEET-PG:** * **Prausnitz-Küstner (PK) Reaction:** A classic (though now obsolete) test used to demonstrate IgE-mediated serum transfer of allergy. * **Casoni’s Test:** An immediate hypersensitivity skin test used for Hydatid disease. * **Key Cytokine:** **IL-4** is the essential cytokine for IgE class switching. * **Atopic Triad:** Asthma, Allergic Rhinitis, and Atopic Dermatitis.

Question 1

Severe combined immunodeficiency is seen with which precursor cell type?

Accepted Answer

Both Pre-B and Pre-T cells

Answer

Pre-B cell

Answer

Pre-T cell

Answer

NK cell precursor

Question 2

Which of the following is found in DiGeorge syndrome?

Accepted Answer

Tetany

Answer

Eczema

Answer

Total absence of T cells

Answer

Absent B and T cells

Question 3

Which of the following are affected in graft versus host reaction?

Accepted Answer

Lung

Answer

Skin

Answer

Gastrointestinal tract

Answer

Liver

Question 4

All are true about Bloom syndrome except?

Accepted Answer

Decreased levels of IgG

Answer

Decreased IgM levels

Answer

Absent IgA

Answer

Raised IgE levels

Question 5

A patient presents with a history of episodic painful edema of the face and larynx, associated with abdominal pain, particularly during periods of stress. Which of the following is likely to be deficient?

Accepted Answer

C1 Esterase Inhibitor

Answer

Complement C3

Answer

Complement C5

Answer

Properidin

Question 6

An infant with a history of delayed separation of the umbilical cord now presents with recurrent pneumonia. The total white blood cell count is 20,000/ml. Which of the following genetic defects is most likely present?

Accepted Answer

Reduced phagocyte surface expression of Sialyl-Lewis x

Answer

Low levels of NADPH oxidase and a negative DHR test

Answer

Mutation of the Bruton tyrosine kinase gene

Answer

Excessive IgM with reduced IgG and IgA

Question 7

Hemolytic disease of the newborn is which type of hypersensitivity reaction?

Accepted Answer

Type II

Answer

Type I

Answer

Type III

Answer

Type IV

Question 8

Hemolytic disease of the newborn is an example of which type of hypersensitivity reaction?

Accepted Answer

Type 2 hypersensitivity reaction

Answer

Type 3 hypersensitivity reaction

Answer

Arthus reaction

Answer

Type 4 hypersensitivity reaction

Question 9

Atopy is primarily mediated by which immunoglobulin class?

Accepted Answer

IgE

Answer

IgD

Answer

IgM

Answer

IgA

Question 10

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

Immunopathology — MCQs

Immunopathology — MCQs

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