Week 1 - J - Immunology of the eye and immune privelage - and sympathetic ophthalmia Flashcards
What are the two types of immunity from the immune system?
Innate - non specific first line response
Acquired - specific and has a memory
The innate and adaptive immune system work synergistically to tackle immune problems How long does the innate immunity take to react vs the acquired?
Innate immunity is a rapid, immediate response
Acquired immunity gradually takes place over a few days
The innate immunity gives a physical barrier for protection eg skin What does the eye lack to give this physical barrier?
It lacks skin over the eye
Due to the eye not being protected from pathogens by innate immunity facotrs such as physical barrier and commonesal bacteria How does it make up for this?
Reflex tears and the chemical properties of tears eg lysozymes
Also reducing the size of the eye to prevent infection from entering
In the inate system of the eye You have the blink reflex and physical properties of the srufce eg tears, have chemical properties and have the immune cells of the eye WHat are the three layers of the tear film of the eye? (what produces each layer)
Have an oily lipid outer layer - meibum produced from tarsal glands in the eylid
Have an aqueous middle layer containing chemicals
Have a mucin layer - mucous produced by the bulbar conjunctivae goblet cells
What is the chemical propery of tears that acts against gram negative and what acts against gram positive?
Lysozyme fights gram negative bacteria and fungi and destroys the cell wall
Lactoferrin and transferrin acts againt gram +ve bacteria
What immunoglobulin is secreted in tears?
IgA
What are the three main immune cells of the eye?
Neutrophils
Macrophages
Conjunctival mast cells
Which of the immune cells helps to trigger the adaptive immune system?
The macrophages
The adaptive immune system requires antigen presenting cells with lymphatic drainage to lymph node and a variety of effector cells What is the main antigen presenting cell in the external eye and skin?
The Langerhans cell
What layer of skin is the langerhans cell most common in?
Most common in the prickle cell layer - stratum spinosum
The langerhan cells are rich in what MHC class?
Righ in MHC Class II - helps activate CD4+
What are MHC II cels important in initiating?
They are important in initiating immune response
Langerhan cells are abundant at corneo-scleral limbus, less in peripheral cornea, where are they absent?
they are absent in the central 1/3rd of the cornea
What is the only part of the eye with lymphatic drainage?
The conjunctiva
What layer of the eye is avascular?
The cornea and sclera
What is the lacrimal drainage system?
They have diffuse lymphoid tissue and follicles (MALT) which drains into the lacrimal punctum
Certain sites of the body are able to tolerate the introduction of antigens without eliciting an inflammatory immune response The eye is one of these sites, what is this known as?
The immune privelage
What sites in the eye are immune privileged? (mnemonic CALVS)
The corrnea
Anterior chamber
Lens
Vitreous cavity
Subretinal space
Ocular immune privilege mechanisms include: Unique anatomical features of a blood-tissue barrier and a lack of direct lymphatic drainage Ocular microenvironment is rich in immunosuppressive molecules and inhibitory cell surface molecules that influence the reactivity of immune cells Anterior chamber-associated immune deviation (ACAID)
What is the blood tissue barrier of the eye?
The choroid and retina
The anterior chamber associated immune deviation has some immunological hallmarks What does it inhibit?
Inhibits the cell mediated immune response (Type IV hypersensitivity)
Rare, bilateral, granulomatous uveitis due to trauma (more common) or surgery (less common) to one eye ?
This is known as sympathetic opthalmia
How does the sympathetic opthalmia begin?
Starts of as uveitis as the immune system is attacking one eye and then the immune system begins to attack the other eye
What is the exciting and sympathetic eye in sympathetic opthalmia?
Exciting eye is the injured eye
Sympathetic eye is the fellow eye
How does the trauma to one eye cause the immune system to release T cells to damage both eyes?
Trauma to on eye ends up with the release of antigens in this eye, they travel to the lymph nodes where Tcells are produced and travel in the bloodstream to affect both eyes
How does sympathetic opthalmia relate to a disadvantage of the immune privelage of the eye?
Relates to the physical and immunological isolation of the eye from the systemic immune system
What parts of the eye has the immune privelage? (recap question) (CALVS)
CALVS
Cornea
Anterior chamber
Lens
Vitreous chamber
Subretinal space
An example of type 1 hypersensitivity condition is allergic conjunctivitis How does this immune process work?
There is always more antibody than antigen produced so when exposed originally to the allergen the IgE antibodies bind to Fc receptors on the mast cells
Next time on exposure the IgE is already formed and this causes degranulation of the mast cells releasing eg histamine
Autoimmune conditions are usually classified as type II hypersensitivty WHat is an example of a type II which is known as a subtype of mucous membrane pemphigoid?
This would be ocular cicatricial pemphigoid
Ocular cicatricial pemphigoid is an autoimmune condition affecting the conjunctivae What can you treat this with?
Can try steroids
Type III hypersensitivity - Autoimmune corneal melting
Outer layer of cornea melting; inner layer bulging forward possible perforation What can perforation cause?
Can massively increase chance of infection as there will be a hole straight to the eye
What are side effects of steroid use in the eye?
Can cause glaucoma by damaging the trabecular meshwork leading to a build up of pressure in the eye
Can denature lens fibres leading to cataracts
