Inflammation and Repair Practice Questions

Q: Which of the following requires calcium for ligand binding?

P-selectin. ***P-selectin*** - **P-selectin** is a **C-type (calcium-dependent) lectin** that requires **Ca²⁺ ions** for its carbohydrate recognition domain to function. - The calcium is essential for maintaining the proper **conformational structure** of the lectin domain, enabling it to bind carbohydrate ligands like **sialyl-Lewis X** on leukocytes. - Expressed on activated endothelial cells and platelets during inflammation. *Sialyl-Lewis X* - This is a **carbohydrate ligand** (not a receptor) found on leukocytes that binds to selectins. - It does not itself require calcium for binding; rather, it is recognized by calcium-dependent selectins. *LFA-1* - **LFA-1** is an **integrin** that binds to ICAMs. - While integrins require **Mg²⁺** (not Ca²⁺) for optimal binding, LFA-1 is not primarily characterized as calcium-dependent for ligand binding. *PSGL-1* - **PSGL-1** is a **glycoprotein ligand** on leukocytes, not a receptor. - It does not require calcium for its own function; the calcium dependency is on the selectin side of the interaction.

Q: Which of the following helps in movement and adhesion?

CD31. ***CD31*** - **CD31 (Platelet Endothelial Cell Adhesion Molecule-1, PECAM-1)** plays a critical role in **leukocyte transendothelial migration**, which is essential for leukocyte movement and adherence to endothelial cells during inflammation. - It mediates both **homophilic and heterophilic binding** at intercellular junctions, facilitating the passage of leukocytes through vessel walls. *PGE2* - **Prostaglandin E2 (PGE2)** is involved in inflammation, primarily causing **vasodilation**, fever, and pain sensitization. - While it modulates immune responses, its primary function is not direct cell movement or adhesion. *MCP1* - **MCP-1 (Monocyte Chemoattractant Protein-1), also known as CCL2**, is a chemokine that primarily functions in **chemoattraction** of monocytes, macrophages, and T cells. - It guides these cells to sites of inflammation but does not directly mediate adhesion to endothelial surfaces. *LTB4* - **Leukotriene B4 (LTB4)** is a potent **chemoattractant for neutrophils**, guiding their migration to inflammatory sites. - Its main function is **chemotaxis**, promoting the directed movement of neutrophils, rather than direct cell adhesion.

Q: Granulomas in lymph nodes are seen in all of the following infections EXCEPT:

Staph Aureus. ***Staph Aureus*** - *Staphylococcus aureus* typically causes **suppurative (pus-forming)** infections leading to **abscesses** and **pyogenic inflammation**, not granulomas [2], [3]. - Lymph node involvement with *S. aureus* usually manifests as **acute lymphadenitis** with neutrophil infiltration, not organized granulomatous structures [2]. *Histoplasmosis* - **Histoplasmosis**, caused by *Histoplasma capsulatum*, is a fungal infection that commonly forms **granulomas** in affected tissues, including lymph nodes [1]. - These granulomas often resemble those seen in tuberculosis and can be **caseating or non-caseating** [1]. *Brucellosis* - **Brucellosis**, caused by *Brucella* species, is a zoonotic bacterial infection that classically forms **non-caseating granulomas** in multiple organs including lymph nodes, liver, and spleen. - The granulomas are characterized by epithelioid histiocytes and may contain multinucleated giant cells. *TB* - **Tuberculosis (TB)**, caused by *Mycobacterium tuberculosis*, is the classic example of an infection that forms **caseating granulomas** in affected lymph nodes [3]. - These granulomas are characterized by **central caseous necrosis** surrounded by epithelioid histiocytes, lymphocytes, and Langhans giant cells [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 592-593. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 360. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 379-380.

Q: Which of the following complement components acts as a chemoattractant?

C5a. ***Correct: C5a*** - **C5a** is a powerful **chemoattractant** for neutrophils, monocytes, and macrophages, guiding them to sites of infection and inflammation. - It also acts as an **anaphylatoxin**, promoting inflammation through mast cell degranulation and histamine release. *Incorrect: C3b* - The primary function of **C3b** is **opsonization**, marking pathogens for phagocytosis by immune cells. - It also plays a crucial role in forming the **C5 convertase** in the complement activation pathways. *Incorrect: C4a* - **C4a** is a weak **anaphylatoxin** involved in modulating inflammation, but its chemotactic activity is minimal. - It is generated during the activation of the **classical** and **lectin pathways** of complement. *Incorrect: C3a* - **C3a** is an **anaphylatoxin** that promotes inflammation by inducing degranulation of mast cells and basophils. - It has some weak chemotactic properties but is considerably less potent than **C5a** in attracting immune cells.

Q: Most effective bactericidal system within phagocytes is-

Reactive oxygen metabolite mediated. ***Reactive oxygen metabolite mediated*** - The production of **reactive oxygen metabolites** (like superoxide, hydrogen peroxide, and hydroxyl radicals) through the **respiratory burst** is a highly potent mechanism for killing phagocytosed bacteria. - These highly reactive molecules cause **oxidative damage** to bacterial components, leading to their degradation and death. *Cationic basic protein mediated* - **Cationic proteins** (e.g., defensins) have antimicrobial properties by damaging bacterial membranes, but they are generally less potent than reactive oxygen species in overall bacterial killing within phagocytes. - While important, they contribute to a broader array of antimicrobial mechanisms but are not considered the *most effective* single system. *Lysozyme mediated* - **Lysozyme** primarily targets bacterial **peptidoglycan**, breaking down bacterial cell walls, especially in gram-positive bacteria. - It is an important antimicrobial enzyme, but its effectiveness is limited against many gram-negative bacteria with outer membranes and it is generally less destructive than the radical-forming reactive oxygen species. *Lactoferrin mediated* - **Lactoferrin** primarily acts by **chelating iron**, which is an essential nutrient for bacterial growth, thereby inhibiting bacterial proliferation. - While important for bacteriostasis, its direct bactericidal activity is often limited compared to the direct damaging effects of reactive oxygen species.

Q: The most important function of epithelioid cells in tuberculosis is -

Secretory. ***Secretory*** - Epithelioid cells are **modified macrophages** characterized by abundant eosinophilic cytoplasm due to increased endoplasmic reticulum and Golgi apparatus [1]. - Their **most important function is secretory** - they actively secrete cytokines (TNF-α, IL-1, IL-12), chemokines, and enzymes that maintain the granuloma structure and modulate the immune response [1]. - These secretory products help **contain the infection**, activate T-cells, and recruit other immune cells to form the organized granuloma [1]. - This secretory function is the defining characteristic that distinguishes them from ordinary macrophages. *Phagocytosis* - While epithelioid cells are derived from macrophages, their differentiation leads to **reduced phagocytic capacity**. - They have less prominent lysosomes and reduced ability to engulf pathogens compared to activated macrophages. - Their primary role has shifted from active phagocytosis to secretion and barrier formation. *Healing* - Epithelioid cells contribute to containment and eventual resolution of infection, but "healing" is not their direct primary function. - Healing involves fibrosis, collagen deposition (by fibroblasts), and tissue remodeling - processes distinct from the epithelioid cell's secretory role. - The granuloma itself (formed by epithelioid cells) may undergo **fibrosis or caseation**, but this is a consequence rather than the primary function. *Antigenic* - While epithelioid cells can present antigens (being derived from antigen-presenting macrophages), this is not their most important function in TB granulomas. - Antigen presentation is mainly carried out by dendritic cells and macrophages at earlier stages of immune response. - The defining role of epithelioid cells is their secretory activity that maintains granuloma structure. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 109.

Q: Caspase involved in activation of IL-1 is which of the following?

Caspase 1. ***Caspase 1*** - **Caspase 1** (also known as interleukin-1 beta converting enzyme or ICE) is the primary caspase responsible for the proteolytic cleavage and activation of pro-IL-1β and pro-IL-18 into their mature, active forms. - This activation occurs within the **inflammasome complex**, a multiprotein oligomer that assembles in response to various pathogens and danger signals. *Caspase 5* - While **Caspase 5** is an inflammatory caspase, similar to Caspase 1, it primarily functions in the direct activation of pro-IL-1β in certain contexts, particularly in response to *Gram-negative bacteria* through the non-canonical inflammasome. - However, **Caspase 1** is the canonical and most well-known activator of IL-1 in the classical inflammasome pathway. *Caspase 8* - **Caspase 8** is a key **initiator caspase** in the extrinsic pathway of apoptosis, activated by death receptors like Fas and TNF receptors. - Its primary role is in **apoptotic signaling** and it is not directly involved in the proteolytic activation of IL-1. *Caspase 3* - **Caspase 3** is a major **effector caspase** in both the intrinsic and extrinsic pathways of apoptosis. - It executes apoptosis by cleaving numerous cellular substrates and is not directly involved in the **processing of cytokines** like IL-1.

Question 1

Which of the following requires calcium for ligand binding?

Accepted Answer

P-selectin

Answer

Sialyl-Lewis X

Answer

LFA-1

Answer

PSGL-1

Question 2

Which of the following helps in movement and adhesion?

Accepted Answer

CD31

Answer

PGE2

Answer

MCP1

Answer

LTB4

Question 3

Granulomas in lymph nodes are seen in all of the following infections EXCEPT:

Accepted Answer

Staph Aureus

Answer

Histoplasmosis

Answer

Brucellosis

Answer

TB

Question 4

Which of the following complement components acts as a chemoattractant?

Accepted Answer

C5a

Answer

C3b

Answer

C4a

Answer

C3a

Question 5

Fibroblasts in healing wound are derived from -

Accepted Answer

Local mesenchyme

Answer

Epithelium

Answer

Endothelium

Answer

Bone marrow

Question 6

Liver after transplant enlarges by -

Accepted Answer

Both

Answer

Increase in number of cells

Answer

Increase in size of cell

Answer

None of the options

Question 7

Most effective bactericidal system within phagocytes is-

Accepted Answer

Reactive oxygen metabolite mediated

Answer

Cationic basic protein mediated

Answer

Lysozyme mediated

Answer

Lactoferrin mediated

Question 8

Asteroid bodies in non-caseating granulomas are characteristically seen in:

Accepted Answer

Sarcoidosis

Answer

Sporotrichosis

Answer

Chromoblastomycosis

Answer

Syphilis

Question 9

The most important function of epithelioid cells in tuberculosis is -

Accepted Answer

Secretory

Answer

Phagocytosis

Answer

Healing

Answer

Antigenic

Question 10

Caspase involved in activation of IL-1 is which of the following?

Accepted Answer

Caspase 1

Answer

Caspase 5

Answer

Caspase 8

Answer

Caspase 3

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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