Immunology Flashcards
Name 2 physical barriers involved in the innate immune system of the eye
The blink reflex
The tear film
Name the layers of the tear film from outer to inner
Lipid layer
Aqueous layer
Mucin layer
Describe each layer of the tear film:
Lipid layer
Aqueous layer
Mucin layer
Lipid layer: produced by the Meibomian glands and prevents evaporation of the aqueous layer
Aqueous layer: produced by the lacrimal glands and contains many anti-microbial chemicals
Mucin layer: sits on the cornea and allows the aqueous layer to stick to the hydrophobic cornea, also prevents adhesion of microbes to the cornea
Name some of the antimicrobial chemicals which are found in the aqueous layer of the tear film
Lysozyme, lactoferrin and transferrin (destroy bacteria)
Tear lipids (act against bacterial products)
Secretory IgA (prevents attachment)
IL-6, IL-8, MIP (recruit leucocytes)
Angiogenin
Complement
What 3 innate immune cells are found in the eye?
Neutrophils
Macrophages
Conjunctival mast cells
What are the 3 basic requirements of the adaptive immune system?
Antigen presenting cells
Lymphatic drainage to lymph nodes
A variety of effector cells
What is the principle antigen presenting cell for the external eye and where is it most commonly found?
Langerhans cells
Most abundant at the corneo-scleral limbus
Less in the peripheral cornea and absent in the central 1/3rd of the cornea
What is the only part of the eye with lymphatic drainage?
The conjunctiva
It is the only part of the eye with MALT (mucosa associated lymphoid tissue) and lymphoid cells e.g., T cells
This makes it important for developing adaptive immunity
List 3 factors which make the cornea and sclera have a downregulated immune environment
Avascular so chemotaxis cannot occur and recruit neutrophils
No lymphatics/lymphoid tissue
Langerhans cells only found in the corneo-scleral limbus and peripheral cornea
The lacrimal glands contain which 2 adaptive immune cells which they insert into tears?
IgA plasma cells
CD8+ T cells
The lacrimal drainage system contains MALT tissue. T/F?
True
Why is the vitreous body (in the posterior segment of the eye) a downregulated immune environment? (2)
There is a lack of immune cells but it is rich in nutrients
This provides a medium for bacteria but no defence against them => this can cause endophthalmitis
Certain sites of the body have ‘immune privilege’. What is meant by this term?
They have a downregulated immune system and so are able to tolerate introduction of antigens without eliciting an inflammatory immune response
The brain/CNS, testes, placenta/foetus, and the eyes are all examples of immune privileged body sites. What sites of the eye are immune privileged?
Cornea Anterior chamber Lens Vitreous cavity Subretinal space (basically everything but the conjunctiva really)
Why is it useful for the eye to have immune privilege?
It helps maintain ocular clarity/good vision
e.g., blood vessels can’t travel through the cornea or we wouldn’t be able to see through it
