Inflammation and Repair Practice Questions

Q: All of the following are true regarding the Arachidonic acid (AA) pathway, except:

Leukotrienes C4, D4 cause vasodilation.. **Explanation:** The Arachidonic Acid (AA) pathway is a central theme in inflammation and pharmacology. This question tests the physiological effects of eicosanoids and the mechanism of AA release. **Why Option D is the correct (False) statement:** Leukotrienes **C4, D4, and E4** (collectively known as cysteinyl leukotrienes) are potent **vasoconstrictors** and **bronchoconstrictors**. They also increase vascular permeability (leading to edema). In contrast, Prostaglandins like $PGI_2$ (Prostacyclin) and $PGE_2$ are the primary mediators that cause vasodilation in this pathway. **Analysis of other options:** * **Option A:** Aspirin is a non-selective, irreversible inhibitor of **Cyclooxygenase (COX-1 and COX-2)**. By inhibiting these enzymes, it prevents the conversion of AA into Prostaglandins and Thromboxanes, thus inhibiting a major branch of the AA pathway. * **Option B:** The rate-limiting step in eicosanoid synthesis is the release of AA from membrane phospholipids. This is mediated by the enzyme **Phospholipase A2 (PLA2)**, which is activated by an increase in **cytosolic $Ca^{2+}$** levels. * **Option C:** Phospholipase A2 acts on membrane phospholipids (like phosphatidylcholine) to cleave and release free **Arachidonic acid**, which then serves as the substrate for COX and LOX enzymes. **NEET-PG High-Yield Pearls:** 1. **LTC4, LTD4, LTE4:** Potent bronchoconstrictors; involved in the pathogenesis of asthma (Slow Reacting Substance of Anaphylaxis - SRS-A). 2. **LTB4:** Primarily involved in **chemotaxis** (attracts neutrophils). 3. **Zileuton:** Inhibits 5-Lipoxygenase (5-LOX), preventing leukotriene synthesis. 4. **Montelukast/Zafirlukast:** Block CysLT1 receptors (antagonists for LTC4, D4, E4). 5. **Steroids:** Inhibit the entire AA pathway by inducing **Lipocortin (Annexin A1)**, which inhibits Phospholipase A2.

Question 1

All of the following are true regarding the Arachidonic acid (AA) pathway, except:

Accepted Answer

Leukotrienes C4, D4 cause vasodilation.

Answer

Aspirin inhibits the arachidonic acid pathway.

Answer

Cytosolic Ca2+ leads to activation of membrane phospholipase A2.

Answer

Action of phospholipase A2 causes synthesis of arachidonic acid.

Question 2

What is the principal mediator of vasodilation in acute inflammation?

Accepted Answer

Histamine

Answer

Serotonin

Answer

IL-1

Answer

TNF

Question 3

Eosinophil production is increased by which of the following cytokines?

Accepted Answer

IL-5

Answer

IL-1

Answer

IL-6

Answer

TNF-A

Question 4

Which of the following describes the oxidative or respiratory burst phenomenon?

Accepted Answer

It involves the activation of NADPH oxidase associated with an increase in oxygen uptake and metabolism in neutrophils.

Answer

It is due to antimicrobial proteins called defensins.

Answer

It occurs during diapedesis.

Answer

It leads to the production of HOCl and HOBr from Cl- and Br- respectively by the action of myeloperoxidase.

Question 5

A 59-year-old man experiences acute chest pain and is rushed to the emergency room. Laboratory studies and ECG demonstrate an acute myocardial infarction; however, coronary angiography performed 2 hours later does not show evidence of thrombosis. Which of the following mediators of inflammation causes relaxation of vascular smooth muscle cells and vasodilation of arterioles at the site of myocardial infarction in this patient?

Accepted Answer

Nitric oxide

Answer

Bradykinin

Answer

Histamine

Answer

Leukotrienes

Question 6

All the following receptors play a role in phagocytosis EXCEPT-

Accepted Answer

G protein coupled receptor

Answer

Mannose receptors

Answer

Scavenger receptors

Answer

Receptors for opsonins

Question 7

Which of the following factors impairs wound healing?

Accepted Answer

Clot formation

Answer

Diabetes mellitus

Answer

Glucocorticoids

Answer

Vitamin C deficiency

Question 8

Which of the following is NOT an endogenous chemoattractant?

Accepted Answer

Integrins

Answer

C5a

Answer

Leukotriene B4 (LTB4)

Answer

Interleukin-8 (IL-8)

Question 9

Hallmark of tuberculous inflammation are all, except:

Accepted Answer

Liquefactive necrosis

Answer

Caseous necrosis

Answer

Langhan's cells

Answer

Epithelioid cell granuloma

Question 10

Cachexin is:

Accepted Answer

TNF

Answer

IL-2

Answer

IL-12

Answer

INF-gamma

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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