Immunology Flashcards
What is different about the innate immune system specific to the eye?
- No physical barrier like the skin => exposed
- Limited commensal bacteria
- Relies on chemical agents and specific cells to provide immunity
What solutions does the eye use to improve its own immunity?
- Blink reflex
- Limit exposure/size
What physical properties of tears contribute to the innate immune system?
Flushing across eye
Mucous layer = anti-adhesive
What chemical properties of tears contribute to the innate immune system of the eye?
- Lysozyme (destroy bacteria cell wall)
- Tear lipids (antibacterial to cell membranes)
- Secretory IgA (prevents attachment)
- IL-6, IL-8 (antimicrobial molecules that recruit leucocytes)
What cellular properties of tears contribute to the innate immune system of the eye?
- Neutrophils = Scavengers – release free radicals, enzymes
- Macrophages = Phagocytosis
- Conjunctival mast cells = Vasoactive mediators
What is the principle antigen presenting cell in the external eye?
Langerhans cell
- type of macrophage
Where are most langerhans cells most abundant in the eye?
corneo-scleral limbus
What is the only part of the eye which contains lymphatic drainage?
conjunctiva
What is found in the conjunctiva instead of lymph nodes?
Mucosa associated lymphoid tissue (MALT)
What are the cornea and sclera mostly composed of?
collagen
The cornea and sclera contain no lymphatics or blood vessels. TRUE/FALSE?
TRUE
avascular and no lymphoid tissue or APCs
What immune cells are found more in the lacrimal gland than in the conjunctiva?
plasma cells (IgA) CD8+ T cells T cells in small groups around intralobar ducts
What is the blood-ocular barrier?
tight junctions preventing movement of structures from blood into the eye
What is meant by an immune privileged site?
tolerates the introduction of antigens without an inflammatory immune response
Other than the eye, where in the body is considered an immune privileged site?
Brain and CNS
Testes
Placenta/Foetus
What sites in the eye are thought to be immune privileged
Cornea Anterior chamber Lens Vitreous cavity Subretinal space
What is meant by anterior chamber associated immune deviation (ACAID)?
- placement of foreign antigen into the ocular microenvironment
- induces a systemic form of tolerance to the foreign antigen
What is meant by sympathetic ophthalmica?
- granulomatous uveitis due to trauma or surgery
- autoimmune reaction to ocular antigens: exposed during the traumatic or surgical event
In sympathetic ophthalmica, what are the affected an non-affected eyes referred to as?
affected = ‘exciting eye’
other eye = ‘sympathising’
What clinical signs may present on examination of the affected eye in sympathetic ophthalmica?
vitreous fluid = hazy
inflamed retina
What can occur if the immune system does not work?
Recurrent infections Allergy Hypersensitivity reactions Autoimmune disease Cancer Transplant/graft rejection
Autoimmune uveoretinitis is an inflammation of what parts of the eye?
uvea and retina
Retina autoantibodies (common in retinopathy associated with cancer/infection/degenerative disease) Sympathetic ophthalmia (bilateral granulomatous uveitis)
What autoimmune process is a Dalen-Fuchs nodule?
epithelial cell clusters in retinal layers
What is the medical term for “dry eyes”?
Keratoconjunctivitis sicca
How can the lens cause uveitis?
Reaction due to release of lens products
When are retinal autoantibodies usually found?
retinopathy associated with cancer/infection/degenerative disease
Give an example of a Type 1 Hypersensitivity reaction in the eye?
Acute allergic conjunctivitis
How does acute allergic conjunctivitis usually present?
chemosis (conjunctival oedema)
itchy inflamed eye
What cells are involved in direct killing during Type 2 Hypersensitivity reactions?
Macrophages/natural killer (NK) cells
Complement (membrane attack complex)
Give an example of a type 2 hypersensitivity reaction in the eye?
ocular cicatricial pemphigoid
How does ocular cicatricial pemphigoid usually present?
blistering and scarring of conjunctiva
Corneal melting can occur as a result of what hypersensitivity type?
Type 3 - Immune complex
What should you worry about on seeing a corneal melt?
possibility of eye perforation
Give an example of a Type IV hypersensitivity reaction
corneal graft rejection
How can you tell that a corneal graft is being rejected by its host?
Vascularisation (blood vessels) of host cornea are growing and almost reaching the donor tissue
What ocular side effects do steroids induce?
Cataracts
Steroid-induced glaucoma
Graft rejection can be saved if acted on quickly. TRUE/FALSE?
TRUE
