Inflammation 2: Leukocyte Recruitment

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Questions and Answers

What is the primary function of chemotaxis in leukocytes?

Release of cytokines into the bloodstream

Movement toward sites of infection along a chemical gradient (correct)

Movement away from sites of infection

Ingestion of foreign particles

Which of the following substances is NOT considered a chemotactic agent for leukocytes?

C5a component of the complement system

Reactive oxygen species (correct)

Bacterial products

Cytokines, especially chemokines

Which type of leukocyte is primarily attracted to viral infections?

Neutrophils

Eosinophils

Monocytes

Lymphocytes (correct)

What is the first step in the process of phagocytosis?

Recognition and attachment of the particle to the ingesting leukocyte Signup and view all the answers

Which of the following correctly describes opsonins?

They enhance the phagocytosis of microbes. Signup and view all the answers

What role do Neutrophil Extracellular Traps (NETs) play in the immune response?

They trap and contain pathogens to prevent their spread. Signup and view all the answers

Which types of reactive substances are involved in the intracellular destruction of microbes?

Reactive oxygen species and lysosomal enzymes Signup and view all the answers

What occurs to neutrophils during the formation of NETs?

They undergo a process of cell death. Signup and view all the answers

Which type of inflammation is characterized by the formation of abundant exudates rich in mucus affecting mucous membranes?

Catarrhal inflammation Signup and view all the answers

In which type of inflammation can you find a membrane structure formed by fibrin threads and necrotic cells?

Pseudo-membranous inflammation Signup and view all the answers

What type of inflammation is characterized by a rich fluid exudate and can be observed in conditions like pleural effusion?

Serous inflammation Signup and view all the answers

What is the first step of leukocyte recruitment from the vascular lumen to the extravascular space?

Margination and rolling along the vessel wall Signup and view all the answers

Which type of inflammation involves hyperemia and edema in the submucosa with infiltration of leucocytes?

Catarrhal inflammation Signup and view all the answers

Which molecules mediate the rolling of leukocytes along the endothelial surface?

Selectins Signup and view all the answers

What characterizes fibrinous inflammation in terms of exudate composition?

Predominance of fibrinogen and fibrin Signup and view all the answers

Which of the following statements accurately describes pseudo-membranous inflammation?

It leaves a bleeding surface when the membrane is removed. Signup and view all the answers

What triggers the activation of integrins on leukocyte surfaces?

Activation by chemokines Signup and view all the answers

Which type of acute inflammation is most commonly associated with localized collections of pus?

Furuncle (boil) Signup and view all the answers

What process allows leukocytes to migrate through the vessel wall?

Squeezing through intercellular junctions Signup and view all the answers

What are chemokines primarily responsible for during leukocyte recruitment?

Stimulating migration towards their chemical gradient Signup and view all the answers

Which condition does not primarily result from type of inflammation involving abundant exudates with high protein content?

Abscess formation Signup and view all the answers

What role do TNF and IL-1 play in the adhesion of leukocytes?

Increasing expression of ligands for integrins Signup and view all the answers

What is the term used for the migration of leukocytes through the endothelium?

Diapedesis Signup and view all the answers

Which substance do leukocytes secrete to facilitate passage through the vascular basement membrane?

Collagenases Signup and view all the answers

What characterizes hemorrhagic inflammation?

Exudate rich in blood Signup and view all the answers

What is the primary causative organism of suppurative inflammation?

Streptococci Signup and view all the answers

What happens if an abscess is not evacuated?

It ruptures at the point of least mechanical resistance Signup and view all the answers

Which of the following correctly describes the composition of pus?

Living and dead microorganisms, dead polymorphs, and liquefied necrotic tissues Signup and view all the answers

What is the primary function of macrophages in inflammation resolution?

To clear exudate and debris Signup and view all the answers

What is a characteristic of allergic inflammation?

Exudation of abundant fluid containing eosinophils Signup and view all the answers

Which statement about abscess healing is false?

Abscess healing leads to permanent tissue loss Signup and view all the answers

Fibrin formation is best described as?

Eosinophilic meshwork or amorphous coagulum Signup and view all the answers

Study Notes

Inflammation 2

Leukocyte Recruitment and Activation
- The series of events for leukocyte recruitment to extravascular space includes margination and rolling along vessel walls, firm adhesion to the endothelium, transmigration between endothelial cells, and migration through interstitial tissues toward a chemotactic stimulus
- Adhesion is mediated by integrins interacting with their ligands on endothelial cells.
- Specific ligands on endothelial cells are activated by TNF and IL-1
- Integrins are low-affinity until activated, then cytoskeleton changes allow firm attachment
Margination
- The accumulation of leukocytes at the periphery of blood vessels
- Rolling: Leukocytes weakly bind and detach from the endothelium, tumbling on the endothelial surface
Rolling
- Weak and transient interactions mediated by selectins (a family of adhesion molecules)
- Types of selectins: E-selectin (on endothelial cells), P-selectin (on platelets and endothelium), and L-selectin (on leukocytes)
Transmigration
- Leukocytes migrate through the vessel wall by squeezing between cells at intercellular junctions (also called diapedesis)
- Leukocyte migration is driven by chemokines, molecules produced in extravascular tissues.
- Leukocytes secrete collagenases to pass through the vascular basement membrane
Chemotaxis
- Leukocytes move towards infection or injury sites along a chemical gradient
- Chemotactic agents include bacterial products, pathogenic organisms, cytokines (especially chemokines), and complement system components (e.g., C5a) and leukotrienes from neutrophils
Types of Emigrating Leukocytes
- Cocci attract PMNLs
- Bacilli attract monocytes
- Viruses attract lymphocytes
- Parasites and hypersensitivity attract eosinophils
Phagocytosis and Clearance
- Ingestion of particulate material by cells
- Three steps: recognition and attachment of the particle, engulfment of the particle to form a phagocytic vacuole, and killing/degradation of the ingested particle
- The most important phagocytes are neutrophils (microphages) and macrophages
- Opsonization enhances phagocytosis
Intracellular Destruction
- Reactive oxygen species (ROS), Reactive nitrogen species (derived from nitric oxide), and Lysosomal enzymes (acid hydrolases and elastase)
Neutrophil Extracellular Traps (NETs)
- Extracellular fibrillar networks produced by neutrophils in response to infectious pathogens, inflammatory mediators
NET Role
- Traps provide high concentrations of antimicrobial substances at infection sites
- Prevents spread of microbes by trapping them in fibrils
- Formation involves nuclear chromatin and granule proteins, such as antimicrobial peptides and enzymes
- Associated with sepsis
Types of Acute Inflammation
- Suppurative (Localized/Diffuse)
  - Abscess: Localized area of suppurative inflammation
  - Furuncle (boil) : Localized suppuration in hair follicle or sebaceous gland
  - Carbuncle (localized) : Suppuration in subcutaneous tissue, with multiple loculi and openings
  - Cellulitis (diffuse): Diffuse suppurative inflammation of subcutaneous tissue, often caused by strep infection.
Types of Acute Inflammation(Continued)
- Non-suppurative
  - Catarrhal: Mild inflammation of mucous membranes, characterized by exudate rich in mucus
  - Pseudo-membranous: Severe inflammation causing a membrane-like structure on mucous surfaces, often due to bacterial toxins
  - Serous: Inflammation characterized by exudation of watery fluid, rich in protein (e.g., pleural effusion, blisters)
  - Fibrinous: Inflammation marked by fibrin accumulation, often in body cavities (e.g., pericardium)
  - Hemorrhagic: Inflammation featuring blood in the exudate, often due to blood vessel damage
  - Allergic: Inflammation triggered by antigen-antibody reactions, characterized by exudate containing eosinophils (e.g., urticaria)
Fate of Abscess
- Rupture at point of least mechanical resistance if not drained
- Healing by granulation tissue after evacuation/drainage
Complications of Abscess
- Ulcers, fistulas, and sinuses
Spread of Infection
- Lymphatic spread (lymphangitis, lymphadenitis)
- Blood spread (toxemia, septicemia, pyaemia)
Chronic Abscess
- Failure of complete drainage

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Description

This quiz covers the processes involved in leukocyte recruitment and activation during inflammation. Topics include margination, rolling, and the roles of integrins and selectins in these processes. Test your understanding of how leukocytes adhere to blood vessels and migrate toward chemotactic stimuli.