Lecture 14: Chronic Inflammation 1

Question 1

What is the definition of chronic inflammation?

2

Answer 1

Inflammation of prolonged duration in which
active inflammation,
tissue destruction
and attempts at repair

occur simultaneously.

Question 2

What are the circumstances of chronic inflammation?

3

Answer 2

1. May arise from unresolved acute inflammation that becomes chronic
2. Often begins insidiously as a smouldering process with no recognisable acute phase
3. Always incited by the persistent presence of:
   - an irritant
   - micro-organism
   - injured tissue or
   - immune response
4. Arise in a variety of circumstances-varied
5. May be sterile or infected

Question 3

Whats the hallmark of chronic inflammation?

4

Answer 3

1. Cellular infiltrate comprised of any of:
	Macrophages
	Lymphocytes
	Plasma cells (lesion > 2 weeks old)
	\+/- neutrophils / eosinophils

2. The infiltrate destroys and replaces tissue
3. Attempts at healing result in proliferation of tissue stroma and abundant fibrosis

Question 4

whats the gross pathology of chronic lesions

5

Answer 4

Gross Pathology of Chronic Lesions
Areas of swelling/ thickening/ nodularity
Fibrosis –> areas appear pale & firm
Cellular infiltration & proliferation areas appear pale, variable texture (firm +/- soft)
Concurrent tissue loss –> organ appears irregular +/- shrunken

Question 5

What is the functions of macrophages on chronic inflammation.
function of dentritic cells?
7

Answer 5

Gross Pathology of Chronic Lesions
Areas of swelling/ thickening/ nodularity
Fibrosis  areas appear pale & firm
Cellular infiltration & proliferation areas appear pale, variable texture (firm +/- soft)
Concurrent tissue loss  organ appears irregular +/- shrunken

Question 6

lymphocytes

8 and 9

Answer 6

Lymphocytes:
Humoral (Ab) and cell mediated immunity.
MØ process and present Ag to naive T lymphocytes, activating them.
Activated T lymphocytes (CD4 T cells = conductor)  lymphokines which act on other lymphocytes.

Lymphocytes:
T lymphocytes: antigen-specific helper and cytotoxic/ suppressor subtypes,
B lymphocytes produce antibodies specific to an antigen.
B lymphocytes that produce specific antibodies appear morphologically different = plasma cells.
Chronic inflammation

Lymphocytes
3. Natural killer cells
= type of lymphocyte (large granular lymphocyte)
~10% of circulating lymphocytes
Innate immune response

Question 7

Function of Fibroblasts

11

Answer 7

Fibroblasts
-main cell type in connective tissue;
-stable cells
-essential to wound repair:
-they can proliferate locally and synthesise extracellular matrix components (eg collagen, fibronectin) to provide structural integrity and tensile strength in wounds.
-rich source of growth factors eg keratinocyte growth factor, IGF-1.
- heterogeneous: e.g. some will gain contractile properties (myofibroblasts) which is critical in wound contraction.
check out slide 12 for histology image

Question 8

Give some examples of chronic inflammation? 13

Answer 8

• Abscess formation
• Foreign body reaction
• Chronic trauma
• Immune mediated chronic inflammation
• Granulomatous inflammation

Question 9

What are the key features of a microbial abscess?

15

Answer 9

1. Persistent inciting agent (bacteria / fungi)
2. Acute inflammatory response (neutrophils) fails to kill the micro-oganism
3. Central necrotic debris (purulent exudate) surrounded by a zone of macrophages/ lymphocytes/plasma cells and encapsulated by fibrous tissue (walled off).

Question 10

What is an abscess sequelae

19

Answer 10

1. Micro-organism is killed – the abscess is organized (replaced by scar tissue),
   becomes a cold abscess
2. Bacteria proliferate
   Purulent exudate accumulates.
   Pressure builds up within the abscess.
   The abscess points and ruptures along the path of least resistance.

Question 11

Two types of abscess rupture:

20

Answer 11

External rupture
Cavity, draining sinus / fistula fills with granulation tissue and heals by 2nd intention.

Internal rupture.
Spread along fascial planes widespread fasciitis / cellulitis
Rupture into a blood vessel or airway

Question 12

What is a Sequestrum?
What is a Involucrum?
26

Answer 12

SequestrumNecrotic bone acts as a foreign bodyInvolucrum Subperiosteal new bone covers the sequestrum

Question 13

Classification of chronic inflammation (based on predominant cell type)
MAcrophages?
Epithelioid macrophages and MNGC ?
Lymphocytes?
Plasma cells?
Lymphocytes and plasma cells?
Neutrophils and epithelioid macrophages?
31

Answer 13

Macrophages = histiocytic

Epithelioid macrophages & MNGC = granulomatous

Lymphocytes = lymphocytic

Plasma cells = plasmacytic

Lymphocytes & plasma cells = lymphoplasmacytic

Neutrophils & epithelioid macrophages = pyogranulomatous.