Inflammation and Repair — MCQs
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An 87-year-old woman has had a cough productive of yellowish sputum for the past 2 days. On examination her temperature is 37°C. A chest radiograph shows bilateral patchy infiltrates. Her peripheral blood shows leukocytosis. A week later she is afebrile. Which of the following is the most likely outcome of her pulmonary disease?
Exudation of plasma and leukocytes in acute inflammation is primarily from which of the following vascular structures?
What best describes Neutrophil Extracellular Traps (NETs)?
Which of the following is not a pyrogenic cytokine?
Which of the following are acute phase reactants in acute inflammation?
Which of the following composes the majority of the leukocyte infiltrate after the first 24 hours of an inflammatory response?
Increased accumulation of fluid in the interstitial space is described as?
In muscle hypertrophy, which myosin isoform changes?
Which is considered the most important pyogenic Interleukin?
Bronchospasm is initiated by?
Inflammation and Repair Indian Medical PG Practice Questions and MCQs
Question 191: An 87-year-old woman has had a cough productive of yellowish sputum for the past 2 days. On examination her temperature is 37°C. A chest radiograph shows bilateral patchy infiltrates. Her peripheral blood shows leukocytosis. A week later she is afebrile. Which of the following is the most likely outcome of her pulmonary disease?
- A. Chronic inflammation
- B. Fibrous scarring
- C. Neoplasia
- D. Resolution (Correct Answer)
Explanation: ### Explanation **Correct Option: D. Resolution** The clinical presentation describes a classic case of **Acute Bronchopneumonia** (productive cough, yellowish sputum, patchy infiltrates, and leukocytosis). The key to this question lies in the patient’s recovery: she became afebrile within a week. **Why Resolution?** Resolution is the restoration of the tissue to its normal state. It occurs when: 1. The injury is limited or short-lived [1]. 2. There is minimal tissue destruction [1]. 3. The tissue has a high regenerative capacity (like the lung parenchyma) [1]. In this case, the rapid clinical improvement (becoming afebrile) and the nature of the exudate (neutrophilic/purulent) suggest that the body successfully cleared the pathogen and the inflammatory debris via liquefaction and resorption, allowing the lung architecture to remain intact [2]. **Analysis of Incorrect Options:** * **A. Chronic Inflammation:** This occurs if the injurious agent persists or if there is an interference with the healing process. The patient’s quick recovery (1 week) rules out a chronic course [1]. * **B. Fibrous Scarring:** This occurs when there is substantial tissue destruction (e.g., an abscess) or when the inflammatory exudate cannot be cleared (organization) [1], [3]. In typical bronchopneumonia, the alveolar basement membranes are preserved, favoring regeneration over scarring. * **C. Neoplasia:** Inflammation does not directly transform into malignancy within a week. While chronic inflammation (e.g., H. pylori) is a risk factor for cancer, acute pneumonia is not a precursor to neoplasia. **NEET-PG High-Yield Pearls:** * **Resolution vs. Organization:** If the exudate in pneumonia is not resolved, it undergoes "organization," where ingrowth of fibroblasts leads to fibrous scarring [3]. * **Key Mediator:** **Macrophage** is the central cell in resolution; it cleans up debris, neutrophils, and fibrin [1], [2]. * **Pneumonia Outcomes:** Lobar pneumonia typically undergoes resolution, whereas complicated bronchopneumonia or lung abscesses often result in scarring [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 103-104. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 193-194. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 194-195.
Question 192: Exudation of plasma and leukocytes in acute inflammation is primarily from which of the following vascular structures?
- A. Venules (Correct Answer)
- B. Capillaries
- C. Arterioles
- D. Arterioles and capillaries
Explanation: **Explanation:** In acute inflammation, the primary site for the exudation of plasma (edema) and the emigration of leukocytes (diapedesis) is the **post-capillary venules** [1], [2]. **Why Venules are the Correct Answer:** The hallmark of acute inflammation is increased vascular permeability [4]. This occurs primarily in the post-capillary venules (measuring 20–60 μm in diameter) due to the high density of receptors for inflammatory mediators like **histamine, bradykinin, and leukotrienes** [1]. These mediators cause endothelial cell contraction, creating "interendothelial gaps" through which fluid and cells escape [1]. Additionally, the lower shear stress in venules compared to arterioles facilitates leukocyte rolling and adhesion [3]. **Analysis of Incorrect Options:** * **Arterioles (C):** These are primarily involved in **vasodilation** (mediated by Nitric Oxide and Prostaglandins), which increases blood flow to the area (rubor and calor), but they are not the main site of leakage [4]. * **Capillaries (B):** While some leakage can occur here in cases of direct endothelial injury (e.g., severe burns), they lack the specific receptor density and structural characteristics that make venules the preferred site for mediator-induced leakage [1]. * **Arterioles and Capillaries (D):** This is incorrect because it excludes the venules, which are the physiologically dominant site for exudation. **High-Yield Clinical Pearls for NEET-PG:** * **Immediate Transient Response:** This is the most common pattern of increased permeability, occurs only in **post-capillary venules**, and lasts for 15–30 minutes [1]. * **Leukocyte Adhesion Cascade:** Remember the sequence: Margination → Rolling (Selectins) → Adhesion (Integrins) → Transmigration (PECAM-1/CD31) [3]. * **Starling’s Hypothesis:** In inflammation, exudation occurs because of increased hydrostatic pressure (due to vasodilation) and decreased osmotic pressure (due to protein leakage) [4]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 187-188. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 188-189. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Migration in the tissues toward a chemotactic stimulus, pp. 86-87. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 84-85.
Question 193: What best describes Neutrophil Extracellular Traps (NETs)?
- A. NETs are extracellular fibrillar networks.
- B. NETs provide a high concentration of antimicrobial substances at sites of infection.
- C. NETs are produced by neutrophils in response to inflammatory mediators.
- D. All of the above (Correct Answer)
Explanation: **Explanation:** Neutrophil Extracellular Traps (NETs) represent a specialized form of innate immune defense where neutrophils "sacrifice" themselves to trap and kill pathogens. * **Option A is correct:** NETs are **extracellular fibrillar networks** composed of a meshwork of nuclear chromatin (DNA and histones). This sticky scaffold physically traps bacteria, fungi, and parasites, preventing their systemic spread. * **Option B is correct:** During the process of **NETosis**, granule proteins (such as myeloperoxidase, elastase, and cathepsin G) are released and bound to the chromatin fibers [1]. This creates a **high local concentration of antimicrobial substances**, allowing for efficient killing of pathogens without relying solely on phagocytosis. * **Option C is correct:** NETs are produced in response to various **inflammatory mediators**, including infectious pathogens (bacteria, fungi), cytokines (IL-8), and chemokines. Since all individual statements accurately describe the structure, function, and induction of NETs, **Option D is the correct answer.** **High-Yield NEET-PG Pearls:** 1. **NETosis:** This is a distinct form of programmed cell death (different from apoptosis and necrosis) where the neutrophil membrane ruptures to release its contents. 2. **Clinical Correlation:** NETs have a "double-edged sword" nature. While they fight infection, they are implicated in **autoimmune diseases** (e.g., SLE, where NET DNA may act as an autoantigen) and **thrombosis** (providing a scaffold for platelet aggregation) [1]. 3. **Key Enzyme:** **PAD4** (Peptidylarginine deiminase 4) is essential for NET formation as it causes histone citrullination, leading to chromatin decondensation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 91-93.
Question 194: Which of the following is not a pyrogenic cytokine?
- A. IL-1
- B. TNF
- C. IFN-a
- D. IL-18 (Correct Answer)
Explanation: The regulation of body temperature is controlled by the hypothalamus. Fever (pyrexia) is mediated by **pyrogens**, which can be exogenous (e.g., bacterial LPS) or endogenous (cytokines) [1]. **Why IL-18 is the correct answer:** While IL-18 belongs to the IL-1 family of cytokines and plays a significant role in the inflammatory cascade (specifically in stimulating IFN-̲ production and Th1 responses), it is **not** a primary pyrogenic cytokine. It does not significantly cross the blood-brain barrier or act on the anterior hypothalamus to induce the synthesis of Prostaglandin E2 (PGE2), the chief mediator of fever. **Analysis of incorrect options:** * **IL-1 (Interleukin-1):** This is the most potent endogenous pyrogen. It induces PGE2 synthesis in the vascular endothelial cells of the hypothalamus [1]. * **TNF (Tumor Necrosis Factor):** A major pyrogenic cytokine that induces fever both directly (acting on the hypothalamus) and indirectly (by stimulating IL-1 release) [1]. * **IFN-̱ (Interferon-alpha):** Along with IL-6, interferons act as endogenous pyrogens. This explains why "flu-like symptoms" (fever and chills) are common side effects of interferon therapy. **NEET-PG High-Yield Pearls:** 1. **The Master Mediator:** PGE2 is the ultimate mediator of fever in the hypothalamus [2]. Aspirin and NSAIDs reduce fever by inhibiting Cyclooxygenase (COX), thereby blocking PGE2 synthesis. 2. **Primary Endogenous Pyrogens:** Remember the triad: **IL-1, TNF, and IL-6.** [1] 3. **Exogenous Pyrogens:** The most common is **LPS (Lipopolysaccharide)** from Gram-negative bacteria, which triggers the release of endogenous cytokines. 4. **IL-18 Function:** Primarily involved in the activation of NK cells and T-cells; it is processed by the **inflammasome** (Caspase-1), similar to IL-1̲ [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 111. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-94. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 196.
Question 195: Which of the following are acute phase reactants in acute inflammation?
- A. Albumin
- B. Fibrinogen
- C. Haptoglobin (Correct Answer)
- D. Gammaglobulin
Explanation: **Explanation:** Acute Phase Reactants (APRs) are proteins whose plasma concentrations increase (Positive APRs) or decrease (Negative APRs) by at least 25% in response to inflammatory cytokines like **IL-6, IL-1, and TNF-α** [1]. **Why Haptoglobin is Correct:** Haptoglobin is a **Positive Acute Phase Reactant**. Its primary function is to bind free hemoglobin released from erythrocytes, preventing oxidative tissue damage and iron loss. During acute inflammation, the liver upregulates its synthesis to limit the availability of iron to invading microbes (nutritional immunity). **Analysis of Incorrect Options:** * **A. Albumin:** This is a **Negative Acute Phase Reactant**. Its levels decrease during acute inflammation as the liver prioritizes the synthesis of positive APRs and because of increased vascular permeability leading to leakage. * **B. Fibrinogen:** While Fibrinogen **is** a positive acute phase reactant (it causes the increased ESR seen in inflammation), in the context of many standardized exams, Haptoglobin or CRP are often prioritized as classic examples. However, if this were a "multiple correct" type question, Fibrinogen would also be right. In a single-best-answer format, Haptoglobin is a highly specific biochemical marker for this category. * **D. Gammaglobulins:** These are produced by plasma cells, not the liver. While they increase in chronic inflammation (polyclonal gammopathy), they are not classified as acute phase reactants. **NEET-PG High-Yield Pearls:** * **Positive APRs:** C-Reactive Protein (fastest rise), Ferritin, Fibrinogen, Haptoglobin, Hepcidin, and Ceruloplasmin. * **Negative APRs:** Albumin, Transferrin, and Transthyretin (Pre-albumin). * **ESR vs. CRP:** CRP is a more sensitive and direct indicator of acute inflammation than ESR, as ESR is indirectly affected by red cell morphology and plasma proteins like fibrinogen. * **Hepcidin's Role:** Increased hepcidin during inflammation sequesters iron in macrophages, leading to **Anemia of Chronic Disease**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-101.
Question 196: Which of the following composes the majority of the leukocyte infiltrate after the first 24 hours of an inflammatory response?
- A. Neutrophil
- B. Monocyte (Correct Answer)
- C. Lymphocyte
- D. Eosinophil
Explanation: In acute inflammation, the cellular infiltrate follows a predictable chronological sequence determined by the expression of adhesion molecules and the lifespan of specific leukocytes [1]. **Why Monocytes are the correct answer:** During the first **6 to 24 hours**, neutrophils predominate because they are more numerous in the blood, respond more rapidly to chemokines, and attach more firmly to adhesion molecules like P-selectin and E-selectin [1]. However, neutrophils are short-lived and undergo apoptosis within 24–48 hours. After the initial **24 to 48 hours**, **monocytes** (which become macrophages in tissue) replace them [1]. Monocytes survive longer, can proliferate in the tissues, and are better equipped for the sustained phagocytosis and repair required in the later stages of inflammation. **Analysis of Incorrect Options:** * **A. Neutrophils:** These are the "first responders" and dominate the infiltrate only during the first 6–24 hours [1]. * **C. Lymphocytes:** These are typically associated with chronic inflammation or specific viral infections (e.g., viral meningitis), rather than the immediate post-24-hour window of a standard acute response. * **D. Eosinophils:** These are the predominant cells in hypersensitivity reactions (Type I) and parasitic infections, but not in general acute inflammation. **High-Yield NEET-PG Pearls:** * **Exceptions to the Rule:** In **Pseudomonas** infections, neutrophils persist for several days. In **viral infections**, lymphocytes may be the first cells to arrive. In **hypersensitivity reactions**, eosinophils may dominate early. * **Key Mediator:** Monocyte recruitment is largely driven by MCP-1 (Monocyte Chemoattractant Protein-1). * **Sequence:** Neutrophils (6–24 hrs) $\rightarrow$ Monocytes/Macrophages (24–48 hrs) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89.
Question 197: Increased accumulation of fluid in the interstitial space is described as?
- A. Edema (Correct Answer)
- B. Effusion
- C. Transudate
- D. Exudate
Explanation: **Explanation:** **Correct Answer: A. Edema** Edema is defined as the **increased accumulation of fluid in the interstitial tissue spaces** [1], [3]. It occurs when the balance of Starling forces (hydrostatic and oncotic pressure) is disrupted, or when lymphatic drainage is impaired, leading to fluid movement from the vascular compartment into the extravascular (interstitial) space [1], [2]. **Analysis of Incorrect Options:** * **B. Effusion:** While similar to edema, an effusion specifically refers to the accumulation of fluid in **serous body cavities** (e.g., pleural, pericardial, or peritoneal cavities) rather than the tissue interstitium [1], [3]. * **C. Transudate:** This is a **type** of edema fluid characterized by low protein content (<3 g/dL) and low specific gravity (<1.012). It occurs due to systemic imbalances (e.g., congestive heart failure or cirrhosis) without increased vascular permeability [2]. * **D. Exudate:** This is a **type** of edema fluid characterized by high protein content (>3 g/dL) and high specific gravity (>1.020). It occurs primarily in inflammatory states where there is increased vascular permeability [4]. **High-Yield Clinical Pearls for NEET-PG:** * **Anasarca:** Severe, generalized edema with widespread subcutaneous tissue swelling. * **Pitting vs. Non-pitting:** Pitting edema is typical of cardiac or renal failure; non-pitting edema is characteristic of lymphatic obstruction (Lymphedema) or Myxedema [1], [5]. * **Key Starling Force Change:** The most common cause of transudative edema is **decreased plasma colloid osmotic pressure** (hypoalbuminemia) or **increased hydrostatic pressure** [2], [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 124-126. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, p. 124. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 124-125. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 126-127. [5] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 125-126.
Question 198: In muscle hypertrophy, which myosin isoform changes?
- A. Alpha (Correct Answer)
- B. Beta
- C. Theta
- D. Delta
Explanation: **Explanation:** In the context of cardiac muscle hypertrophy (a form of cellular adaptation), the heart undergoes structural and molecular changes to handle increased workload. The correct answer is **Alpha-myosin**, as it is the isoform that undergoes a specific molecular switch. **1. Why Alpha is Correct:** In a normal adult heart, the **Alpha-myosin heavy chain ($\alpha$-MHC)** is the predominant isoform. It is characterized by high ATPase activity, allowing for rapid contraction. During hypertrophy (e.g., due to hypertension or valvular disease), there is a **"fetal gene program" induction**. This causes a switch from the Alpha-isoform to the **Beta-isoform ($\beta$-MHC)**. The Beta-isoform has lower ATPase activity, leading to slower, more energetically economical contractions. Therefore, the Alpha isoform is the one that "changes" (decreases) during this adaptive process. **2. Why other options are incorrect:** * **Beta:** While the Beta-isoform increases, the question asks which isoform *changes* its expression pattern from the baseline adult state. In the context of pathology textbooks (like Robbins), the focus is on the downregulation of the Alpha-isoform. * **Theta and Delta:** These are not standard myosin heavy chain isoforms found in human cardiac muscle adaptation. They are distractors. **NEET-PG High-Yield Pearls:** * **Hypertrophy vs. Hyperplasia:** Muscle cells (cardiac and skeletal) undergo hypertrophy only because they are permanent cells with limited replicative capacity [1]. * **Molecular Switch:** Hypertrophy is not just an increase in size; it involves the re-expression of fetal genes like **ANP (Atrial Natriuretic Peptide)** and $\beta$-MHC. * **Trigger:** The primary mechanical trigger for hypertrophy is the activation of stretch-sensitive sensors (integrins) and trophic factors (IGF-1). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Cellular Responses to Stress and Toxic Insults: Adaptation, Injury, and Death, pp. 46-47.
Question 199: Which is considered the most important pyogenic Interleukin?
- A. IL-2
- B. IL-1 (Correct Answer)
- C. IL-6
- D. IL-8
Explanation: **Explanation:** The correct answer is **IL-1**. This cytokine is the primary endogenous pyrogen responsible for inducing fever (pyrexia) during inflammation [1]. **1. Why IL-1 is correct:** IL-1 (specifically IL-1̢) is produced by activated macrophages [3]. It travels through the bloodstream to the **hypothalamus**, where it stimulates the production of prostaglandins [1]. This leads to the synthesis of **Prostaglandin E2 (PGE2)**, which resets the hypothalamic thermoregulatory set-point to a higher level, resulting in fever [2]. While IL-6 and TNF-̡ also contribute to fever, IL-1 is considered the most potent and "classic" pyogenic interleukin. **2. Why the other options are incorrect:** * **IL-2:** Primarily functions as a T-cell growth factor. It stimulates the proliferation and differentiation of T-lymphocytes and NK cells but does not have a direct pyogenic effect. * **IL-6:** While IL-6 is a major inducer of the **Acute Phase Response** (stimulating the liver to produce CRP, Fibrinogen, and SAA) [1], it is secondary to IL-1 in the hierarchy of fever induction. * **IL-8:** This is the most important **chemotactic factor** for neutrophils [4]. Its primary role is recruiting neutrophils to the site of inflammation (chemokinesis), not inducing fever. **High-Yield Clinical Pearls for NEET-PG:** * **Endogenous Pyrogens:** IL-1, TNF-̡, and IL-6 [1]. * **Exogenous Pyrogen:** Bacterial Lipopolysaccharide (LPS/Endotoxin), which triggers the release of IL-1. * **Mechanism of Antipyretics:** Aspirin and NSAIDs reduce fever by inhibiting COX, thereby blocking the synthesis of PGE2 in the hypothalamus. * **IL-1 and Osteoclasts:** In bone pathology, IL-1 is also known as **Osteoclast Activating Factor (OAF)**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 111. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 101. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 196. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 97-99.
Question 200: Bronchospasm is initiated by?
- A. C5a
- B. C3a
- C. Leukotrienes (Correct Answer)
- D. Acetylcholines
Explanation: **Explanation:** **Leukotrienes (C4, D4, and E4)**, also known as the **Slow-Reacting Substances of Anaphylaxis (SRS-A)**, are the most potent mediators of bronchospasm [1]. Derived from arachidonic acid via the 5-lipoxygenase pathway, they are significantly more potent than histamine in inducing smooth muscle contraction in the airways [2]. They also increase vascular permeability and stimulate mucus secretion, making them central to the pathogenesis of bronchial asthma [1], [2]. **Analysis of Options:** * **C3a and C5a (Options A & B):** Known as **Anaphylatoxins**, these components of the complement system primarily cause mast cell degranulation (releasing histamine) and chemotaxis (especially C5a) [3]. While they indirectly contribute to inflammation, they are not the primary initiators of sustained bronchospasm. * **Acetylcholine (Option D):** While acetylcholine is a neurotransmitter that causes bronchoconstriction via muscarinic receptors (parasympathetic pathway), it is not considered a primary inflammatory mediator in the context of the cellular response to injury or allergy usually discussed in pathology [1]. **High-Yield Clinical Pearls for NEET-PG:** * **LTC4, LTD4, LTE4:** Cause intense bronchospasm and increased vascular permeability [2]. * **LTB4:** A potent **chemotactic agent** for neutrophils (Mnemonic: LTB4 = "B" for "Be there" / Neutrophil recruitment) [2]. * **Pharmacology Link:** **Montelukast** and **Zafirlukast** are leukotriene receptor antagonists (LTRAs) used in asthma management to block these specific effects. * **Lipoxins:** Unlike leukotrienes, lipoxins (LXA4, LXB4) serve to **inhibit** inflammation (anti-inflammatory). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 688-689. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 95-96. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 95.
Practice by Chapter
Acute Inflammation: Vascular Events
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Acute Inflammation: Cellular Events
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Chemical Mediators of Inflammation
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Chronic Inflammation
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Granulomatous Inflammation
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Systemic Effects of Inflammation
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Wound Healing
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Tissue Regeneration
Practice Questions
Fibrosis and Repair
Practice Questions
Resolution of Inflammation
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