Inflammation and Repair Practice Questions

Q: In the lipoxygenase pathway of arachidonic acid metabolism, which of the following products promotes platelet aggregation and vasoconstriction?

Thromboxane A2. The metabolism of arachidonic acid occurs via two primary pathways: the **Cyclooxygenase (COX) pathway** and the **Lipoxygenase (LOX) pathway**. [1] 1. **Why Thromboxane A2 (TXA2) is correct:** TXA2 is a potent product of the **Cyclooxygenase pathway** (specifically synthesized by platelets). It acts as a powerful **vasoconstrictor** and a mediator of **platelet aggregation** [3]. While the question mentions the "lipoxygenase pathway," TXA2 is the only option listed that performs the physiological functions of vasoconstriction and aggregation. (Note: In competitive exams like NEET-PG, if a question contains a technical inaccuracy in the stem—as TXA2 is a COX product—you must prioritize the functional description provided). 2. **Analysis of Incorrect Options:** * **Leukotriene B4 (LTB4):** This is a product of the **Lipoxygenase pathway** [2]. Its primary role is **chemotaxis** (recruiting neutrophils to inflammation sites). It does not cause platelet aggregation. * **C5a:** This is a component of the **Complement system**. It is a potent anaphylatoxin and chemotactic agent but is not a metabolite of arachidonic acid. * **C1 activators:** These are proteins involved in the initiation of the classical complement pathway, unrelated to arachidonic acid metabolism. **High-Yield Clinical Pearls for NEET-PG:** * **Prostacyclin (PGI2):** Produced by vascular endothelium; it is the functional antagonist to TXA2, causing **vasodilation** and **inhibiting** platelet aggregation. * **Aspirin:** Irreversibly inhibits COX-1, leading to decreased TXA2 production, which explains its use as an anti-platelet "blood thinner" [2]. * **Leukotrienes (C4, D4, E4):** Known as the "Slow-reacting substances of anaphylaxis," they cause intense bronchoconstriction and increased vascular permeability [2].

Q: Which leukotriene functions as an adhesion factor for neutrophils on the cell surface to attach to the endothelium?

Leukotriene B4. ### Explanation **Correct Option: A. Leukotriene B4 (LTB4)** Leukotriene B4 is a potent inflammatory mediator derived from arachidonic acid via the **5-lipoxygenase pathway**. Its primary role in the inflammatory response is the **recruitment and activation of neutrophils**. Specifically, LTB4 functions as a powerful **chemotactic agent** and an **adhesion factor**. It induces the expression of adhesion molecules (integrins) on the surface of neutrophils, facilitating their firm attachment to the vascular endothelium before they undergo diapedesis (transmigration) into the tissues. **Why the other options are incorrect:** * **Leukotriene C4, D4, and E4 (Option B, C, D):** These are collectively known as **cysteinyl leukotrienes** (or the Slow-Reacting Substance of Anaphylaxis - SRS-A). Their primary physiological effects include intense bronchoconstriction, increased vascular permeability (edema), and mucus secretion. They are central to the pathogenesis of bronchial asthma but do not play a significant role in neutrophil adhesion or chemotaxis. --- ### High-Yield Clinical Pearls for NEET-PG: * **Chemotactic "Big Four":** Remember the four most important substances that attract neutrophils: **LTB4**, **IL-8**, **C5a**, and **Bacterial products** (N-formyl methionine). * **Pharmacology Link:** **Zileuton** inhibits 5-lipoxygenase (preventing all LT synthesis), while **Montelukast/Zafirlukast** are receptor antagonists specifically for the cysteinyl leukotrienes (LTC4, LTD4, LTE4). * **LTB4 vs. LTC4/D4/E4:** Think of **LTB4** as "Neutrophil **B**olting" (adhesion/chemotaxis) and **LTC4/D4/E4** as "**C**onstriction" (bronchospasm).

Q: Which cytokine activates the given cell?

Interleukin-5 (IL-5). ***Interleukin-5 (IL-5)*** - **IL-5** is the primary cytokine responsible for **eosinophil activation**, differentiation, and survival from bone marrow precursors. - It specifically promotes **eosinophil recruitment** to tissues and enhances their **degranulation** and cytotoxic functions. *Interleukin-1 (IL-1)* - **IL-1** is a pro-inflammatory cytokine that primarily activates **macrophages** and **endothelial cells**. - It plays a key role in **fever induction** and **acute phase response**, not eosinophil activation. *Interleukin-2 (IL-2)* - **IL-2** is the primary growth factor for **T lymphocytes**, promoting their proliferation and activation. - It has minimal direct effect on **eosinophil function** and is mainly involved in **adaptive immunity**. *Interleukin-6 (IL-6)* - **IL-6** is a pleiotropic cytokine that primarily stimulates **B cell differentiation** and **hepatic acute phase protein synthesis**. - While it has some inflammatory effects, it does not specifically **activate eosinophils** like IL-5 does.

Question 1

What is the most important role of bradykinin in acute inflammation?

Accepted Answer

Increase in vascular permeability

Answer

Vasodilatation

Answer

Mediation of pain

Answer

Bronchoconstriction

Question 2

Which of the following blood vessels is most likely to be affected by endothelial cell retraction?

Accepted Answer

Venules

Answer

Capillaries

Answer

Arterioles

Answer

None of the above

Question 3

Which of the following factors stimulates fibroblast proliferation?

Accepted Answer

TGF-β

Answer

IFN-γ

Answer

TNF-α

Answer

IL-10

Question 4

In the lipoxygenase pathway of arachidonic acid metabolism, which of the following products promotes platelet aggregation and vasoconstriction?

Accepted Answer

Thromboxane A2

Answer

C5a

Answer

Leukotriene B4

Answer

C1 activators

Question 5

Which of the following are stable cells?

Accepted Answer

Mesenchymal cells

Answer

The lining mucosa of the glands

Answer

Nerve cells

Answer

Stratified squamous epithelium of the oral cavity

Question 6

Which leukotriene functions as an adhesion factor for neutrophils on the cell surface to attach to the endothelium?

Accepted Answer

Leukotriene B4

Answer

Leukotriene C4

Answer

Leukotriene D4

Answer

Leukotriene E4

Question 7

Which of the following host tissue responses is NOT seen in acute infection?

Accepted Answer

Granuloma formation

Answer

Exudation

Answer

Vasodilation

Answer

Margination

Question 8

A 35-year-old man has had increasing dyspnea for the past 24 hours. A chest radiograph shows large, bilateral pleural effusions. Thoracentesis yields 500 mL of slightly cloudy yellow fluid from the right pleural cavity. Cytologic examination of the fluid shows many neutrophils, but no lymphocytes or RBCs. Which of the following mechanisms contributes most to the pleural fluid accumulation?

Accepted Answer

Endothelial contraction

Answer

Arteriolar vasoconstriction

Answer

Inhibition of platelet adherence

Answer

Lymphatic obstruction

Question 9

Which cytokine activates the given cell?

Accepted Answer

Interleukin-5 (IL-5)

Answer

Interleukin-1 (IL-1)

Answer

Interleukin-2 (IL-2)

Answer

Interleukin-6 (IL-6)

Question 10

Which of the following substances most likely has the greatest affinity for neutrophils?

Accepted Answer

C5a

Answer

Fucosyl transferase

Answer

P-selectin

Answer

TNF-a

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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