Inflammation

Question 1

What is inflammation?

Answer 1

Inflammation is a protective biological process designed to remove damaged cells and clear threats such as infections and toxins. It can occur in any vascularized tissue and it involves not only cells at the site of damage but also the recruitment immune cells, fluid and molecular components from the circulation.

Question 2

How is inflammation initiated?

Answer 2

It is initiated when cellular damage (non-apoptotic cell death) leads to the release of damage associated molecular patterns (DAMPs) or the body detects pathogen associated molecular patterns (PAMPs).

Question 3

What is the aim of immune cell recruitment?

Answer 3

The aim of immune cell recruitment is to clear the source of the initial inflammatory signal, and eventual resolution and repair of the inflamed tissue. As a result, inflammation has a characteristic pathology associated with the presence of increased fluid and leukocyte numbers.

Question 4

What are the 5 cardinal signs of inflammation?

Answer 4

Rubor - redness
Calor - heat
Tumor - swelling
Dolor - pain
Functio laesa - loss of function

Question 5

What are the 5 steps of inflammation?

Answer 5

1. The process of inflammation is initiated by resident immune cells already present in the involved tissue such as mast cells, macrophages and dendritic cells. These cells posses pattern recognition receptors which bind to pathogen associated molecular patterns or damage associated molecular patterns.
2. These cells become activated and release inflammatory mediators responsible for the clinical signs of inflammation. Vasodilation increases blood flow leading to the redness and heat. This is caused by the mediators histamine and nitric oxide.
3. Increased permeability of the blood vessels results in an exudation of plasma proteins and fluid into the tissue which causes the swelling. This is caused by histamine.
4. Some of the released mediators also increase the sensitivity to pain (hyperalgesia) caused by prostaglandins and cytokines such as TNF.
5. Some mediator molecules also alter the blood vessels to allow the recruitment and migration of leukocytes such as neutrophils and macrophages outside of blood vessels into the tissue. The white blood cells migrate along a chemotactic gradient created by chemokines and complement proteins towards the site of injury.

Question 6

What are the 4 steps of neutrophil extravasation?

Answer 6

1. Chemo-attraction
2. Rolling adhesion
3. Firm adhesion
4. Diapedeses

Question 7

Characteristics of acute inflammation?

Answer 7

Immediate onset

Lasts a few days

Vasodilation, increased vascular permeability, leukocyte response

Neutrophils predominate

Histamine release

Prominent necrosis

Outcomes include:

1. Complete resolution
2. Progression to chronic

Question 8

Characteristics of chronic inflammation?

Answer 8

Delayed onset

Lasts weeks, months or years

Persistent inflammation, ongoing tissue injury, attempts at healing

Monocytes/macrophages predominate

Ongoing cytokine release

Prominent scarring

Outcomes include:

1. Scarring
2. Loss of function