General Pathology Practice Questions

Q: Which of the following is/are a product(s) of the lipoxygenase pathway?

Leukotrienes. **Explanation:** The metabolism of **Arachidonic Acid (AA)** occurs via two major enzymatic pathways: the Cyclooxygenase (COX) pathway and the Lipoxygenase (LOX) pathway [1]. 1. **Why Leukotrienes are correct:** The **5-Lipoxygenase (5-LOX)** enzyme acts on arachidonic acid to produce 5-HPETE, which is subsequently converted into **Leukotrienes (LTs)** [1]. Specifically, LTB4 is a potent chemotactic agent, while LTC4, LTD4, and LTE4 (cysteinyl leukotrienes) cause intense bronchoconstriction and increased vascular permeability [2]. Another branch of the LOX pathway produces **Lipoxins**, which serve as anti-inflammatory mediators. 2. **Why other options are incorrect:** * **Prostaglandins (Option A), Thromboxane A2 (Option B), and Prostacyclin (Option D)** are all products of the **Cyclooxygenase (COX-1 and COX-2)** pathway [2]. * COX converts AA into Prostaglandin G2/H2, which is then converted by specific synthases into PGE2, PGD2, PGF2̱, PGI2 (Prostacyclin), and TxA2 (Thromboxane) [2]. **NEET-PG High-Yield Pearls:** * **Chemotaxis:** LTB4 is one of the most potent chemotactic agents for neutrophils (Mnemonic: **B**4 "**B**rings" neutrophils) [2]. * **Aspirin-Exacerbated Respiratory Disease (AERD):** Inhibiting the COX pathway with Aspirin can "shunt" arachidonic acid toward the LOX pathway, leading to an overproduction of leukotrienes and resulting in bronchospasm [2]. * **Pharmacology Link:** **Zileuton** inhibits 5-Lipoxygenase, while **Montelukast/Zafirlukast** are leukotriene receptor antagonists (CysLT1 receptor) used in asthma management [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-94. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 95.

Q: Which CD marker is characteristic of NK cells?

CD16. **Explanation:** Natural Killer (NK) cells are innate lymphoid cells that play a crucial role in the host defense against tumors and virally infected cells [1]. They are morphologically identified as **Large Granular Lymphocytes (LGLs)**. **Why CD16 is correct:** NK cells are phenotypically defined by the expression of **CD16** and **CD56**, while being negative for CD3 (a T-cell marker). * **CD16** is the low-affinity Fc receptor for IgG (FcγRIII). It allows NK cells to bind to antibody-coated target cells, leading to **Antibody-Dependent Cellular Cytotoxicity (ADCC)**. * **CD56** (NCAM) is the other primary marker used to identify NK cells in flow cytometry. **Analysis of Incorrect Options:** * **CD60:** This is a carbohydrate antigen (sialylated ganglioside) found on a subset of T-cells and melanocytes; it is not a primary diagnostic marker for NK cells. * **CD32:** Also known as FcγRII, this is an inhibitory receptor found primarily on B-cells, macrophages, and neutrophils, but not typically used to identify NK cells. * **CD25:** This is the alpha chain of the **IL-2 receptor**. It is a classic marker for **Regulatory T-cells (Tregs)** and activated T/B cells, rather than resting NK cells. **High-Yield Clinical Pearls for NEET-PG:** 1. **NK Cell Markers:** CD16, CD56, and CD94. They lack CD3, CD4, and TCR. 2. **Mechanism of Killing:** NK cells use **Perforins** (create pores) and **Granzymes** (induce apoptosis). 3. **Chediak-Higashi Syndrome:** Characterized by a profound defect in NK cell function due to impaired degranulation. 4. **Inhibitory Receptors:** NK cells possess **KIR (Killer Immunoglobulin-like Receptors)** which recognize MHC Class I molecules on healthy cells to prevent "self" destruction [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 200-201.

Question 1

Which of the following is a cause of tumorogenesis in aging?

Accepted Answer

Telomerase reactivation

Answer

Telomerase inactivation

Answer

Increased apoptosis

Answer

Suppression of proto-oncogenes

Question 2

Which of the following is/are a product(s) of the lipoxygenase pathway?

Accepted Answer

Leukotrienes

Answer

Prostaglandin

Answer

Thromboxane A2

Answer

Prostacyclin

Question 3

SMAC/DIABLO is a:

Accepted Answer

Pro-apoptotic protein

Answer

Anti-apoptotic protein

Answer

Induces necrosis

Answer

Acts both as anti- and pro-apoptotic protein

Question 4

Cystic fibrosis is inherited as an autosomal recessive condition. A normal couple has one daughter affected with the disease. They are now planning to have another child. What is the chance of her sibling being affected by the disease?

Accepted Answer

1/4

Answer

0

Answer

1/2

Answer

3/4

Question 5

Which CD marker is characteristic of NK cells?

Accepted Answer

CD16

Answer

CD60

Answer

CD32

Answer

CD25

Question 6

The type of immunological reaction seen in endothelial corneal graft rejection is:

Accepted Answer

Type IV

Answer

Type II

Answer

Type III

Answer

Type I

Question 7

Which of the following conditions exhibits autosomal inheritance?

Accepted Answer

Marfan syndrome

Answer

Hemophilia

Answer

Congenital Heart Disease (CHD)

Answer

Gout

Question 8

Delicate, brown or black pigmented non-carious plaque found on the enamel at the cervical margin of the tooth is:

Accepted Answer

Mesenteric line

Answer

Burtonian line

Answer

Argyria

Answer

Bismuth line

Question 9

Angelman syndrome is due to what type of genetic mechanism?

Accepted Answer

Uniparental disomy

Answer

Digenic inheritance

Answer

Inversions

Answer

Mitochondrial disorder

Question 10

Pearl's stain is used to demonstrate which of the following in tissues?

Accepted Answer

Hemosiderin

Answer

Fat

Answer

Reticulin

Answer

Fibrin

General Pathology — MCQs

General Pathology — MCQs

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