Inflammation and Repair Practice Questions

Q: An open wound contracts by what mechanism?

Fibroblast proliferation. **Explanation:** The contraction of an open wound is a critical physiological process aimed at reducing the surface area of the defect. This is primarily mediated by **myofibroblasts**, which are specialized cells derived from **fibroblast proliferation** and differentiation. 1. **Why Fibroblast Proliferation is Correct:** During the proliferative phase of wound healing (typically days 3–14), fibroblasts migrate into the wound. Under the influence of cytokines like TGF-β, these fibroblasts transform into myofibroblasts. These cells contain smooth muscle-like actin filaments (alpha-smooth muscle actin), allowing them to exert contractile forces that pull the wound edges together. 2. **Why Other Options are Incorrect:** * **Stretching of surrounding tissues:** While the surrounding skin may stretch to accommodate the closure, it is a *result* of the contraction, not the primary mechanism driving it. * **Epithelial growth:** This refers to **epithelialization**, where keratinocytes migrate from the edges to cover the surface. This provides a barrier but does not physically pull the wound edges together (contraction). * **Skin grafting:** This is a surgical intervention used to close large wounds; it is not a natural physiological mechanism of contraction. **Clinical Pearls for NEET-PG:** * **Key Cell:** The **Myofibroblast** is the hallmark cell of wound contraction. * **Primary Intention vs. Secondary Intention:** Wound contraction is much more pronounced in healing by **secondary intention** (open wounds). * **Complication:** Excessive contraction can lead to **contractures**, commonly seen after severe burn injuries, which can restrict joint mobility. * **Growth Factor:** **TGF-β** is the most important cytokine stimulating fibroblast-to-myofibroblast differentiation.

Q: Which of the following statements is NOT true about cytokines?

Cytokines participate in intrinsic enzymatic reactions.. Cytokines are low-molecular-weight soluble proteins or **polypeptides** that act as mediators of inflammation and immune responses [1]. **Why Option D is the Correct Answer (The False Statement):** Cytokines do **not** possess intrinsic enzymatic activity. Unlike enzymes, they function by binding to specific high-affinity cell surface receptors. This binding triggers intracellular signaling cascades (most commonly the **JAK-STAT pathway**) to alter gene expression. They act as signaling molecules rather than catalysts for biochemical reactions. **Analysis of Other Options:** * **Option A:** Cytokines are indeed **polypeptides** produced by various cells, primarily activated lymphocytes, macrophages, and dendritic cells [1]. * **Option B:** They exhibit multiple modes of action: **Autocrine** (acting on the cell that secreted them), **Paracrine** (acting on adjacent cells), and occasionally **Endocrine** (systemic effects, e.g., IL-1 and TNF causing fever). * **Option C:** A specific subset of cytokines called **Chemokines** (e.g., IL-8) is responsible for stimulating leukocyte chemotaxis and controlling leukocyte movement from the blood into tissues [1]. **High-Yield NEET-PG Pearls:** * **TNF and IL-1:** The "master cytokines" of acute inflammation; they induce the expression of adhesion molecules (E-selectin) on endothelium. * **JAK-STAT Pathway:** The most common signaling pathway for cytokine receptors; mutations in this pathway are linked to myeloproliferative neoplasms. * **Pleiotropy:** The ability of one cytokine to act on multiple cell types (e.g., IL-4 acting on B-cells, T-cells, and mast cells). * **Redundancy:** Multiple cytokines exerting the same functional effect [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-99.

Q: Leukotrienes are secreted by which of the following cells, except?

Platelets. **Explanation:** The correct answer is **Platelets**. **1. Understanding the Core Concept:** Leukotrienes (LTs) are potent inflammatory mediators derived from **Arachidonic Acid** via the **5-Lipoxygenase (5-LOX) pathway**. The enzyme 5-LOX is primarily expressed in cells of myeloid origin, specifically **leukocytes** (neutrophils, eosinophils, basophils, monocytes/macrophages) and certain **lymphocytes**. **Platelets**, however, lack the 5-LOX enzyme. Instead, they utilize the **Cyclooxygenase (COX)** pathway to produce Thromboxane A2 and the **12-Lipoxygenase** pathway to produce 12-HETE. While platelets can participate in "transcellular biosynthesis" (taking LTA4 from neutrophils to make LTC4), they cannot synthesize leukotrienes independently from arachidonic acid. **2. Analysis of Options:** * **Macrophages (Option A):** These are myeloid cells rich in 5-LOX and are major producers of LTB4 and cysteinyl leukotrienes during chronic inflammation. * **T4 (Helper) and T8 (Cytotoxic) cells (Options B & C):** Research has confirmed that both CD4+ and CD8+ T-lymphocytes possess the enzymatic machinery to produce leukotrienes, which play a role in modulating the adaptive immune response and T-cell trafficking. **3. High-Yield Clinical Pearls for NEET-PG:** * **LTB4:** A potent **chemotactic agent** for neutrophils (mnemonic: LTB4 "B"inds neutrophils). * **LTC4, LTD4, LTE4:** Known as the **Slow-Reacting Substance of Anaphylaxis (SRS-A)**; they cause intense bronchoconstriction and increased vascular permeability. * **Zileuton:** A drug that inhibits 5-Lipoxygenase. * **Montelukast/Zafirlukast:** Leukotriene receptor antagonists (specifically for the CysLT1 receptor) used in asthma management.

Question 1

C-Reactive protein is not raised in which of the following conditions?

Accepted Answer

Viral fever

Answer

Rheumatic fever

Answer

Active rheumatoid arthritis

Answer

Acute gout

Question 2

A clean and small wound heals by which intention?

Accepted Answer

Primary intention

Answer

Secondary intention

Answer

Tertiary intention

Answer

All of the above

Question 3

Which of the following is an anti-inflammatory mediator?

Accepted Answer

Interleukin 4

Answer

Interleukin 1

Answer

Interleukin 6

Answer

TNF-Alpha

Question 4

An open wound contracts by what mechanism?

Accepted Answer

Fibroblast proliferation

Answer

Stretching of surrounding tissues

Answer

Epithelial growth

Answer

Skin grafting

Question 5

Which of the following statements is NOT true about cytokines?

Accepted Answer

Cytokines participate in intrinsic enzymatic reactions.

Answer

Cytokines are polypeptides.

Answer

Cytokines can exert autocrine and paracrine effects.

Answer

Cytokines are involved in leukocytic movements.

Question 6

Which of the following is NOT a role of histamine in acute inflammation?

Accepted Answer

Causes vasoconstriction

Answer

Mediates increase in vascular permeability

Answer

Mediates chemotaxis

Answer

Facilitates release of pain-causing substances

Question 7

All of the following are true for exudates, except?

Accepted Answer

It has a low fibrin content

Answer

It has a specific gravity of 1.018

Answer

It has more than 3% proteins

Answer

It is mucinous in consistency

Question 8

During internal injury, leukocytes are recruited by which of the following?

Accepted Answer

IL-1

Answer

Selectin

Answer

Integrin

Answer

IL-6

Question 9

What are the most characteristic features of acute inflammation?

Accepted Answer

Vasodilation and increased vascular permeability

Answer

Vasoconstriction

Answer

Vascular stasis

Answer

Margination of leukocytes

Question 10

Leukotrienes are secreted by which of the following cells, except?

Accepted Answer

Platelets

Answer

Macrophages

Answer

T4 cells

Answer

T8 cells

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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