Acute Inflammation-Chemotaxis, Phagocytosis, Specific morphologic patterns and Outcomes of inflammation

Question 1

What is chemotaxis❓

Answer 1

Chemotaxis is the movement of leukocytes to the site of injury

Question 2

On what principle do chemotactic agents work❓

Answer 2

Chemotactic agents bind to cell surface receptors and cause activation of phospholipases

Question 3

Classify chemotactic agents and give examples

Answer 3

Endogenous:
C5a
Leukotriene B4
IL-8

Exogenous:
Soluble bacterial products eg N-formylmethionine termini

Question 4

Mention the process involved in phagocytosis

Answer 4

1. Recognition and attachment of particle by leukocyte
2. Engulfment of particle (phagosome—phagolysosome)
3. Killing and degradation

Question 5

Phagocytosis can occur by oxygen dependent mechanisms.

Explain what this entails

Answer 5

In neutrophils…

1. NADPH oxidase:
   oxidizes NADPH
   Reduces oxygen to superoxide ion (oxidative burst)
2. Superoxide ion➡️Hydrogen peroxide (H2O2) by spontaneous dismutation
   3a. H2O2 is acted upon by myeloperoxidase (in presence of Cl- to form hypochlorite ion (OCl-)
   b. H2O2 is also converted to hydroxyl radical (•OH)

Question 6

Which amongst the microbial killing mechanisms of neutrophils is the most effective?

Answer 6

The H2O2-MPO-HALIDE system

Question 7

Where is the enzyme “myeloperoxidase” found❓

Answer 7

In the azurophilic granules of neutrophils

Question 8

List the phagocytic oxygen independent mechanisms of neutrophils

Answer 8

BPI, Bactericidial permeability increasing protein:
Phospholipase activation
Phospholipase degradation
⬆️vascular permeability

Lysozyme:
Degradation of bacterial coat oligosaccharides

MBP, Major Basic Protein:
Cytotoxic component of eosinophil granules

Defensins:
Pore-forming antibacterial peptides

Question 9

What are the morphological patterns of acute inflammation❓

Answer 9

Arteriolar vasodilation 
⬆️vascular permeability 
Transudation and exudation 
Vascular stasis
Accumulation of leukocytes

Question 10

Special morphologic changes may be found in sites of inflammation depending on:

Answer 10

Severity
Cause
Tissue
Site ….. of injury

Question 11

List the special morphologic patterns of acute inflammation

Answer 11

1. Serous inflammation
2. Fibrinous inflammation
3. Suppurative Inflammation

Question 12

Talk briefly about abscesses

Answer 12

• Localized areas of purulent inflammation caused by suppuration buried in a tissue
• Collections of pus formed by pyogenic bacteria
• Central region of necrosis (necrotic neutrophils and tissue cells

Then preserved neutrophils

Then parenchymal cells and fibroblasts (Chronic inflammation and repair)

Question 13

What are the outcomes of inflammation

Answer 13

1. Complete resolution
2. Healing by connective tissue replacement
3. Progression to chronic inflammation

Question 14

What processes are involved in a complete resolution of an acute inflammation❓

Answer 14

• Elimination of offending agent
• Site of injury returns to original state
• Occurs when injury is short-lived, there’s little tissue destruction and damaged parenchymal cells regenerate
• Removal of microbes and cellular debris by macrophages
• Resorption of edema by lymphatics

Question 15

What processes are involved in healing by connecting tissue replacement after an acute inflammation❓

Answer 15

• Substantial tissue destruction
• Tissues are incapable of regeneration
• Abundant fibrin exudation in tissue and cannot be adequately cleared
• Connective tissue is deposited within area of damage converting to fibrous tissue ( a process know as organization)

Question 16

What leads to a progression to chronic inflammation after an acute inflammation❓

Answer 16

• acute inflammatory response can not be resolved
• persistence of injurious agent
• interference with healing process

Question 17

What would one see morphologically in a serous inflammation❓

Answer 17

• Found in peritoneal, pleural and pericardial cavities

* Marked by outpouring of thin fluid from plasma or secretions of mesothelial cells

Question 18

What would one see morphologically (grossly and microscopically) in a fibrinous inflammation❓

Answer 18

• found in lining of body cavities such as meninges, pericardium and pleura
• develops when there are large vascular leaks of fibrinogen or there is a local procoagulant stimulus eg cancer cells
• On histology, fibrin is seen as an eosinophilic meshwork of threads

Question 19

What would one see morphologically a suppurative inflammation❓

Answer 19

• characterized by formation of pus which consists of neutrophils and debris from liquefactive necrosis
• Pyogenic bacteria eg staphylococci produce this localized suppuration
• eg in acute appendicitis