8: Immunology and the eye Flashcards
What are the two types of immunity?
Innate immunity - non-specific
Adaptive immunity - specific
Does the eye have a physical barrier to infection?
No skin
But conjunctiva and cornea
How does the eye clear pathogens?
Blink reflex
What helps to flush pathogens off the surface of the eye?
Lacrimal fluid
Aqueous fluid
Mucus
What are the main cells of the innate immune system?
Neutrophils
Macrophages (link innate and adaptive)
Which cells, found in the conjuncitva, release inflammatory mediators when they degranulate?
Mast cells
Which cells act as antigen presenting cells?
Macrophages
Dendritic cells
B cells
What is a type of macrophage specific to the eye?
Langerhans cell
What is the principle antigen presenting cell of the eye?
Langerhans cell
Where are most Langerhans cells found?
Limbus
What is the only part of the eye with lymphatic drainage?
Conjunctiva
The cornea and sclera are (vascular / avascular).
avascular
What type of lymphatic tissue is found in the lacrimal drainage system?
MALT
What is immune privilege?
Some parts of body tolerate antigens without initiating an inflammatory immune response
What are some areas of the body which have immune privilege?
EYES
Testes
Placenta / foetus
What is ACAID?
Anterior chamber-associated immune deviation
If you put an antigen in the anterior chamber, it is ignored systemically
Why is ACAID useful?
Stops your eye blowing up with inflammation
What happens when immune privilege breaks down?
Eye damage > visual loss
What is sympathetic ophthalmia?
BILATERAL granulomatous uveitis
caused by trauma in ONE EYE
Which famous person had sympathetic ophthalmia?
Louis Braille
What is thought to cause sympathetic ophthalmia?
Immune privilege problem causing an autoimmune reaction in both eyes
Which cells are the primary mediators of sympathetic ophthalmia?
T cells
In sympathetic ophthalmia, what names are given to
a) the injured eye
b) the other eye?
a) Exciting eye
b) Sympathetic eye
Which T cells mediate the
a) early
b) late phases of sympathetic ophthalmia?
a) CD4+ T cells
b) CD8+ T cells
What is the mechanism of sympathetic ophthalmia?
a) Trauma releases intraocular antigens which were there originally
b) Helper T cells transport antigen to lymph nodes
c) Activated cytotoxic T cells return to BOTH eyes, encounter antigen and cause an inflammatory reaction
What diseases are caused by failure of the eye’s immune system?
Recurrent infection
Allergy
Hypersensitivity
Autoimmune disease
Cancer
What is hypersensitivity?
Immune response causing collateral damage
What mediates Type I hypersensitivity reactions?
IgE
which activates mast cells and causes release of inflammatory mediators
What is an example of a Type I hypersensitivity disease of the eye?
Allergic conjunctivitis
What is chemosis?
Conjunctival oedema
What mediates Type II hypersensitivity reactions?
Antibodies
What is an example of a Type II hypersensitivity disease of the eye?
Ocular cicatrial pemphigoid
blistering of the eye
treated using steroids
What mediates Type III hypersensitivity reactions?
Immune complexes
type III - autoimmune corneal melting
What mediates Type IV hypersensitivity reactions?
T cells
“cell mediated”
What are examples of Type IV hypersensitivity diseases?
Corneal transplant rejection
What type of drug is used to counteract inflammatory eye diseases?
Steroid
What are some ocular side effects of steroids?
Cataracts (clouding of the cornea)
Glaucoma (increased intraocular pressure damaging the optic nerve)
