What is chemosis?
Oedema of the conjunctiva
How do the blink reflex and physical properties of the eye surface provide an immunological barrier?
- Mucous layer is an anti-adhesive
Acute allergic conjunctivitis is an example of which type of hypersensitivity?
How do mast cells become activated?
Possess receptors for Fc region of IgE antibody on their surface
Which immune cells are present in the eye and tears?
- Conjunctival mast cells
What does the term "immune privilege" mean?
Refers to area of the body which can tolerate foreign antigens without eliciting an immune response
(e.g. some areas of brain/CNS, testes, placenta/foetus and eyes)
What is sympathetic ophthalmia?
Bilateral diffuse granulomatous uveitis of both eyes following trauma to one eye
Can leave patient completely blind
Symptoms may develop from days to several years after a penetrating eye injury
Autoimmune corneal melting is an example of which type of hypersensitivity reaction?
What is the correct term to describe "dry eyes"?
How are cells killed in a type 2 hypersensitivity response?
- Macrophages/NK cells
- Complement (membrane attack complex)
How is the expression of MHC class I and II different in the corneal cells?
Reduced and impaired expression
Why does an allergic reaction occur?
- After exposure to allergen, IgE antibodies are produced
- They clear away the allergen
- Remaining IgE binds to mast cells via the Fc region
- Subsequent encounters with the allergen cause huge amounts of mast cell degranulation as the IgE binds to the allergen disrupting the cell membrane of mast cell
- Histamine, tryptase, cytokines etc are released
Which areas of the eye may be classed as downregulated immune environments?
What are the immunological hallmarks of anterior chamber associated immune deviation (ACAID)?
- Generation of primed CD4+ T and B cells which produce non-complement fixing antibodies
Inhibition of delayed hypersensitivity (CD4+ and Th1 cells) which secrete complement fixing antibodies
What is the only part of the eye with lympathatic drainage?
What are two serious side effects of steroid use in the eye?
- Steroid induced glaucoma
Why is ACAID required in the eye?
Protects eye and visual axis from collateral damage of immune response to infection
What is MALT?
Mucosa Associated Lymphoid Tissue
(found in the conjunctiva)
Where are Langerhans cells particularly abundant within the eye?
A corneal graft rejection is which type of hypersensitivity reaction?
Why does sympathetic ophthalmia affect both eyes?
- Trauma to one eye releases intraocular antigens into the systemic bloodstream
- Intraocular antigens are carried to lymph nodes
T cells are activated
- Effector T cells infiltrate both eyes where the corresponding antigen can be found
Ocular cicatrical pemphigoid is an example of which type of hypersensitivity reaction?
Which chemical properties of the eye surface contribute to the innate immune system of the eye?
- Lactoferrin and transferrin
- Tear lipids
- Secretory IgA
- IL-6, IL-8 and MIP
What is the principle antigen presenting cell for the external eye?