Pathogenesis Of Inflammatory Eye Disease Flashcards
What is inflammation?
The response of living tissue to damaging stimuli, direct immune comments to site of damage and contain damage and initiate repair
Name six causes of inflammation
1) Infection
2) Hypersensitivity reactions
3) Autoimmunity
4) Trauma
5) Chemical/toxic
6) Radiation
What are five signs of inflammation
1) Redness
2) Pain
3) Warmth
4) Swelling
5) Loss of function
What is the mechanism of acute inflammation?
Vascular events (vasodilation, increased blood flow, increased permeability—> leads to oedema, movement of inflammatory cells from BV to site of injury)
cellular events (involved in initiation and propagation) —> Leukocytes move into tissue, under influence of inflammatory mediators marination occurs, rolling into vessel wall = DIAPEDESIS
What triggers acute inflammation?
Inflammatory mediators which are involved in the initiation and prorogation
What are four major features of an inflammatory response and how do they correspond to the signs of inflammation?
- Vasodilation = redness
- Increased blood flow= heat
- Increased vascular permeability = swelling/oedema
- Movement of inflammatory cells to site of injury –> minimise damage
What are the first cells to migrate to site of injury in an acute inflammatory response?
Neutrophils
What is margination?
Under the influence of inflammatory mediators, the inflammatory cell moves from the center of the blood column to the endothelial wall of the blood vessel
How does an inflammatory cell stick on to the blood cell wall?
By adhesion molecules which are expressed by the endothelium
What is the process which describes the inflammatory cells squeezing through the vessel wall?
Diapedesis
Name the three process which describes an inflammatory cell exiting a blood vessel.
Margination, rolling and diapedesis
What is chemotaxis?
Once a inflammatory cell leaves a BV, it moves along concentration gradients and inflammation chemicals
What is the role of a phagocyte and how is this achieved?
Eliminate pathogens or damages tissues which is done by them attaching to microorganisms via surface receptors, after the binding, it is phagocytsed and destroyed = PHAGOCYTOSIS
What enhances phagocytosis?
Antibodies and the complement system of proteins= OPSONIZATION
What is an opsonin?
An antibody which binds to foreign organisms to make them more susceptible to phagocytosis
What primarily controls the vascular and cellular events?
Chemical mediators which are produced from inflammatory cells
What cells produce vasoactive amines (e.g histamine serotonin)?
Mast cells and basophils
What is an example of a vasoactive amine?
Histamine serotonin
Name four inflammatory mediators and give examples of them.
1) Vasoactive amines –> histamine serotonin
2) Plasma protease –> complement, kinins
3) Arachidonic acid metabolites (eicosanoids)
4) Cytokines –> produced by lymphocytes
Explain the process of eicosanoid synthesis
1) Phosoplipids are converted into arachidonic acid
2) Arachidonic acid is then converted into a variety of inflammatory mediators
3) One example is the enzyme lipoxygenase converts AA to leukotrienes
4) Another example is the enzymes cyclo-oxygenase converts AA to prostaglandins, throboxane which is involved in initiation and propagation
Where are mast cells found in the eye and what type of inflammation cause is it involved in?
The conjunctiva and involved in hypersensitivity reactions
What do mast cells contain?
Granules containing pre formed mediators such as histamine and heparin and neutral protease
What does a release of mediators cause?
Vasodilation and increased vascular permeability
What are the three possible outcomes of acute inflammation?
- Complete resolution
- Scar formation (depends on how much scare tissue is formed)
- Progress to chronic inflammation
Injection is a sign of what?
Vasodilation
What are ocular responses to inflammation?
- Redness
- Oedema
- Exudates (KPs)
- Cellular infiltration ( acute=neutrophils, chronic= macrophages and lymphocytes)
- Discharge (serous, mucopurulent and purulent)
- Conjunctival papillae and follicles
- Inflammation of the posterior segment
What is flare caused by?
Protein entering the aqueous humor due to a breakdown of the blood aqueous barrier- has a cloudy appearance
What are KPs?
Inflammatory cells leaving the vascular system and circulate the aqueous humor to then be deposited in a clump on corneal endothelium
What eye disease is papillae common in?
Allergic eye disease
What eye conditions can inflammation of the posterior segment indicate?
Anterior ischaemic optic neuropathy and sarcodosis
What is an ocular autoimmune disease?
Uveitis
What is sympathetic ophthalmia?
It is followed after a penetrating injury that effects both eyes within three weeks to a year.
What mechanisms lead to cell and tissue damage in autoimmune disease?
1) Autoreactive T-helper cells initiate cell damage due to the production of cytokines
2) Autoreactive cytotoxic T cells also cause tissue damage
3) Autoanitbodies cause tissue by type II mechanism
What is a t-helper cell?
They sense infection they activate other immune cells to fight
do you know the types of hypersensitivity reactions 1-4?
No- then go through it
What two types of hypersensitivity reactions cause allergic eye disease?
Type I and Type IV
What is another word for Type 1 hypersensitivity reaction and what is it caused by?
Mast cell mediated hypersensitivity reaction and is caused by overproduction of IgE
