Inflammation and Repair Practice Questions

Q: During angiogenesis, what factors are responsible for the recruitment of pericytes and periendothelial cells?

Angiopoietins, TGF & PDGF. ***Angiopoietins, TGF & PDGF*** - **Angiopoietins** are crucial for the stabilization of blood vessels and recruitment of **pericytes**, enhancing vessel maturation [1]. - **TGF (Transforming Growth Factor)** and **PDGF (Platelet-Derived Growth Factor)** also play significant roles in the recruitment and proliferation of **pericytes** and periendothelial cells during angiogenesis [1]. *VEGF & PDGF* - While **VEGF (Vascular Endothelial Growth Factor)** is important for endothelial cell migration and proliferation, it does not directly recruit **pericytes** alone. - This combination lacks **angiopoietins**, which are key for the stabilization of newly formed blood vessels [1]. *VEGF, IL-2, IL-6* - **IL-2** and **IL-6** are primarily associated with immune responses and do not directly contribute to pericyte recruitment during angiogenesis. - **VEGF** alone supports endothelial cells but does not effectively recruit **pericytes** without the cooperation of other factors. *TGF, VEGF & PDGF* - Although both **TGF** and **PDGF** are involved in pericyte recruitment [1], the absence of **angiopoietins** limits the effectiveness of this combination for the recruitment process. - **VEGF** alone does not facilitate direct recruitment of **pericytes**, as it mainly focuses on endothelial cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 115-116.

Q: In the context of tissue repair, which cell type is predominantly found during the proliferative phase of wound healing?

Fibroblasts. ***Fibroblasts*** - During the proliferative phase, **fibroblasts** are stimulated to proliferate and migrate into the wound site [1], [2]. - They are responsible for synthesizing and depositing the **extracellular matrix**, including **collagen**, which forms the structural framework of the new tissue [1], [2]. *Mesenchymal cells* - **Mesenchymal cells** are multipotent **stem cells** that can differentiate into various cell types, including fibroblasts, but they are not the predominant cell type actively laying down collagen in the proliferative phase. - While they play a role in providing cells for wound repair, **fibroblasts** are the primary effector cells of collagen production [1]. *Odontoblast* - **Odontoblasts** are specialized cells found in the **dental pulp** that are responsible for forming **dentin**. - They are not involved in general tissue repair processes outside of tooth development or injury. *Ameloblast* - **Ameloblasts** are cells responsible for forming **tooth enamel** during tooth development. - They are not found in general wound healing and are specific to **enamel genesis**. **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. 105-106. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 115-119.

Q: Most important for diapedesis is

PECAM. ***Platelet Endothelial Cell Adhesion Molecule (PECAM)*** - PECAM plays a crucial role in the process of **diapedesis**, allowing white blood cells to pass through the endothelial barrier [1]. - It is specifically involved in **intercellular junctions**, facilitating the migration of leukocytes during **inflammation** [1]. *Selectins* - Selectins are important for **rolling** of leukocytes on the endothelium but do not directly mediate **diapedesis**. - They are crucial for initial attachment but do not promote the passage through the endothelial cell junctions. *Mucin like glycoprotein* - While mucin like glycoproteins can facilitate **cell adhesion**, they primarily contribute to the **rolling phase** rather than diapedesis itself. - They are not as directly involved in the **transmigration** across the endothelium as PECAM. *Integrins* - Integrins are involved in **firm adhesion** of leukocytes, but do not directly enable **diapedesis** across the endothelium. - They support the binding to the endothelium but play a lesser role compared to PECAM in the actual process of migration. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 87-89.

Q: The tensile strength of a wound after laparoscopic cholecystectomy in a 30-year-old woman depends upon:

Extensive crosslinking of tropocollagen. ***Extensive crosslinking of tropocollagen*** - Tensile strength is significantly enhanced by the **crosslinking of tropocollagen**, which stabilizes the collagen matrix in the wound [1]. - This process is crucial for the **maturation phase** of wound healing, leading to increased strength over time [1]. *Replacement of type 3 collagen* - Although type 3 collagen is replaced by type 1 during healing, the mere replacement does not directly contribute to **tensile strength** at the early stages. - Type 1 collagen's eventual predominance is important, but it is **crosslinking** that ultimately determines strength [1]. *Granulation tissue* - Granulation tissue is important for wound healing as it provides a framework for new tissue, but it does not directly correlate with **tensile strength**. - It serves more as a temporary scaffold until collagen remodeling occurs, hence its role in strength is indirect. *Macrophage activity/invasion* - While macrophages are essential for **phagocytosis** and **regulating inflammation**, they do not directly affect the tensile strength of the wound. - Their role is more about initiating the healing process rather than contributing to the **structural integrity** of mature scars. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 119-121.

Q: During phagocytosis, the metabolic process called respiratory burst involves the activation of which?

Oxidase. ***Oxidase*** - During the **respiratory burst**, phagocytes activate **NADPH oxidase** (also known as phagocyte oxidase). - This enzyme catalyzes the production of **superoxide radicals** (O2-•), a highly reactive oxygen species critical for killing ingested pathogens. *Hydrolase* - **Hydrolases** are enzymes that catalyze the hydrolysis of chemical bonds, often found in lysosomes. - While lysosomal enzymes are involved in digestion within phagosomes, they are not directly responsible for the initial production of reactive oxygen species during the **respiratory burst**. *Dehydrogenase* - **Dehydrogenases** are enzymes that catalyze the removal of hydrogen atoms from a substrate, typically transferring them to an electron acceptor. - While some dehydrogenases are involved in metabolic pathways that provide precursors for the respiratory burst, they are not the enzyme directly activated to produce reactive oxygen species in the burst itself. *Peroxidase* - **Peroxidases**, such as **myeloperoxidase (MPO)**, are involved in the subsequent steps of the respiratory burst, using hydrogen peroxide (H2O2) to generate other toxic compounds like hypochlorous acid (HOCl). - However, the initial activation to produce the first reactive oxygen species (superoxide) is carried out by **NADPH oxidase**, not a peroxidase.

Q: The acute inflammatory response is predominantly mediated by which type of immune cells?

Neutrophils. ***Neutrophils*** - **Neutrophils** are the **primary mediators** of the **acute inflammatory response**, being the first immune cells recruited to sites of injury or infection (usually within minutes to hours) [1], [3]. - They are **innate immune cells** that perform phagocytosis, release antimicrobial substances, and form neutrophil extracellular traps (NETs) to combat pathogens [1]. - Neutrophils constitute **50-70% of circulating leukocytes** and are the hallmark cells found in acute inflammation [3]. *T lymphocytes* - **T lymphocytes** are central to **cell-mediated immunity** in the adaptive immune response, requiring several days for activation and clonal expansion [2]. - They recognize specific antigens through TCRs and are not involved in the immediate, non-specific phase of acute inflammation. - T cells play roles in **chronic inflammation** and coordinating adaptive immunity, not acute responses. *B lymphocytes* - **B lymphocytes** mediate **humoral immunity** by producing antibodies during the adaptive immune response [1]. - Their activation, differentiation into plasma cells, and antibody production take days to weeks, making them irrelevant to the rapid acute inflammatory response. - B cells are not recruited to acute inflammatory sites in the initial phase. *Both B and T lymphocytes* - While both are critical for **adaptive immunity** and host defense, neither B nor T lymphocytes are primary mediators of acute inflammation [4]. - The acute inflammatory response relies on **innate immune cells** (neutrophils, macrophages, mast cells) for immediate, non-specific protection before adaptive immunity develops [4].

Q: In a patient with Chronic Granulomatous Disease (CGD) experiencing recurrent bacterial and fungal infections, which specific function of phagocytic leukocytes is primarily impaired due to a defect in the NADPH oxidase system?

Production of reactive oxygen species. ***Production of reactive oxygen species*** - Chronic Granulomatous Disease (CGD) is characterized by a defect in the **NADPH oxidase system**, which is crucial for generating a **respiratory burst**. - This respiratory burst is essential for producing **reactive oxygen species (ROS)** like superoxide radicals, which are vital for killing phagocytosed bacteria and fungi [1]. *Migration to infection sites* - The ability of phagocytes to **migrate to infection sites (chemotaxis)** is generally intact in CGD patients. - Defects in migration are more typically associated with conditions like **Leukocyte Adhesion Deficiency**. *Phagocytosis of pathogens* - Phagocytes in CGD can **engulf pathogens (phagocytosis)** normally [1]. - The defect lies in the **intracellular killing** mechanism *after* phagocytosis, not in the uptake itself [1]. *Presentation of antigens to lymphocytes* - Antigen presentation is a function primarily of **antigen-presenting cells (APCs)** like dendritic cells and macrophages, which is generally unaffected in CGD. - This process is crucial for initiating an **adaptive immune response**, a separate function from the innate pathogen killing defect in CGD. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 91.

Question 1

An elderly man gets a burn injury to his hands. Over several weeks, the burned skin heals without the need for skin grafting. The most critical factor responsible for the rapid healing in this case is:

Accepted Answer

Remnant skin appendages

Answer

Underlying connective tissues

Answer

Minimal edema and erythema

Answer

Granulation tissue

Question 2

During angiogenesis, what factors are responsible for the recruitment of pericytes and periendothelial cells?

Accepted Answer

Angiopoietins, TGF & PDGF

Answer

VEGF & PDGF

Answer

VEGF, IL-2, IL-6

Answer

TGF, VEGF & PDGF

Question 3

The commonest variety of acute inflammation is:

Accepted Answer

Serous inflammation

Answer

Necrotic inflammation

Answer

Catarrhal inflammation

Answer

Purulent inflammation

Question 4

In the context of tissue repair, which cell type is predominantly found during the proliferative phase of wound healing?

Accepted Answer

Fibroblasts

Answer

Mesenchymal cells

Answer

Ameloblasts

Answer

Odontoblasts

Question 5

Most important for diapedesis is

Accepted Answer

PECAM

Answer

Selectins

Answer

Mucin like glycoprotein

Answer

Integrins

Question 6

The tensile strength of a wound after laparoscopic cholecystectomy in a 30-year-old woman depends upon:

Accepted Answer

Extensive crosslinking of tropocollagen

Answer

Granulation tissue

Answer

Macrophage activity/invasion

Answer

Replacement of type 3 collagen

Question 7

During phagocytosis, the metabolic process called respiratory burst involves the activation of which?

Accepted Answer

Oxidase

Answer

Hydrolase

Answer

Dehydrogenase

Answer

Peroxidase

Question 8

The acute inflammatory response is predominantly mediated by which type of immune cells?

Accepted Answer

Neutrophils

Answer

T lymphocytes

Answer

Both B and T lymphocytes

Answer

B lymphocytes

Question 9

In a patient with Chronic Granulomatous Disease (CGD) experiencing recurrent bacterial and fungal infections, which specific function of phagocytic leukocytes is primarily impaired due to a defect in the NADPH oxidase system?

Accepted Answer

Production of reactive oxygen species

Answer

Migration to infection sites

Answer

Phagocytosis of pathogens

Answer

Presentation of antigens to lymphocytes

Inflammation and Repair — MCQs

Inflammation and Repair — MCQs

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