Immunology

Question 1

What is different about the innate immune system specific to the eye?

Answer 1

• No physical barrier like the skin => exposed
• Limited commensal bacteria
• Relies on chemical agents and specific cells to provide immunity

Question 2

What solutions does the eye use to improve its own immunity?

Answer 2

• Blink reflex

- Limit exposure/size

Question 3

What physical properties of tears contribute to the innate immune system?

Answer 3

Flushing across eye

Mucous layer = anti-adhesive

Question 4

What chemical properties of tears contribute to the innate immune system of the eye?

Answer 4

• Lysozyme (destroy bacteria cell wall)
• Tear lipids (antibacterial to cell membranes)
• Secretory IgA (prevents attachment)
• IL-6, IL-8 (antimicrobial molecules that recruit leucocytes)

Question 5

What cellular properties of tears contribute to the innate immune system of the eye?

Answer 5

• Neutrophils = Scavengers – release free radicals, enzymes
• Macrophages = Phagocytosis
• Conjunctival mast cells = Vasoactive mediators

Question 6

What is the principle antigen presenting cell in the external eye?

Answer 6

Langerhans cell

- type of macrophage

Question 7

Where are most langerhans cells most abundant in the eye?

Answer 7

corneo-scleral limbus

Question 8

What is the only part of the eye which contains lymphatic drainage?

Answer 8

conjunctiva

Question 9

What is found in the conjunctiva instead of lymph nodes?

Answer 9

Mucosa associated lymphoid tissue (MALT)

Question 10

What are the cornea and sclera mostly composed of?

Answer 10

collagen

Question 11

The cornea and sclera contain no lymphatics or blood vessels. TRUE/FALSE?

Answer 11

TRUE

avascular and no lymphoid tissue or APCs

Question 12

What immune cells are found more in the lacrimal gland than in the conjunctiva?

Answer 12

plasma cells (IgA) 
CD8+ T cells 
T cells in small groups around intralobar ducts

Question 13

What is the blood-ocular barrier?

Answer 13

tight junctions preventing movement of structures from blood into the eye

Question 14

What is meant by an immune privileged site?

Answer 14

tolerates the introduction of antigens without an inflammatory immune response

Question 15

Other than the eye, where in the body is considered an immune privileged site?

Answer 15

Brain and CNS
Testes
Placenta/Foetus

Question 16

What sites in the eye are thought to be immune privileged

Answer 16

Cornea
Anterior chamber
Lens
Vitreous cavity
Subretinal space

Question 17

What is meant by anterior chamber associated immune deviation (ACAID)?

Answer 17

• placement of foreign antigen into the ocular microenvironment
• induces a systemic form of tolerance to the foreign antigen

Question 18

What is meant by sympathetic ophthalmica?

Answer 18

• granulomatous uveitis due to trauma or surgery

- autoimmune reaction to ocular antigens: exposed during the traumatic or surgical event

Question 19

In sympathetic ophthalmica, what are the affected an non-affected eyes referred to as?

Answer 19

affected = ‘exciting eye’

other eye = ‘sympathising’

Question 20

What clinical signs may present on examination of the affected eye in sympathetic ophthalmica?

Answer 20

vitreous fluid = hazy

inflamed retina

Question 21

What can occur if the immune system does not work?

Answer 21

Recurrent infections
Allergy
Hypersensitivity reactions
Autoimmune disease
Cancer
Transplant/graft rejection

Question 22

Autoimmune uveoretinitis is an inflammation of what parts of the eye?

Answer 22

uvea and retina

Retina autoantibodies (common in retinopathy associated with cancer/infection/degenerative disease)
Sympathetic ophthalmia (bilateral granulomatous uveitis)

Question 23

What autoimmune process is a Dalen-Fuchs nodule?

Answer 23

epithelial cell clusters in retinal layers

Question 24

What is the medical term for “dry eyes”?

Answer 24

Keratoconjunctivitis sicca

Question 25

How can the lens cause uveitis?

Answer 25

Reaction due to release of lens products

Question 26

When are retinal autoantibodies usually found?

Answer 26

retinopathy associated with cancer/infection/degenerative disease

Question 27

Give an example of a Type 1 Hypersensitivity reaction in the eye?

Answer 27

Acute allergic conjunctivitis

Question 28

How does acute allergic conjunctivitis usually present?

Answer 28

chemosis (conjunctival oedema)

itchy inflamed eye

Question 29

What cells are involved in direct killing during Type 2 Hypersensitivity reactions?

Answer 29

Macrophages/natural killer (NK) cells

Complement (membrane attack complex)

Question 30

Give an example of a type 2 hypersensitivity reaction in the eye?

Answer 30

ocular cicatricial pemphigoid

Question 31

How does ocular cicatricial pemphigoid usually present?

Answer 31

blistering and scarring of conjunctiva

Question 32

Corneal melting can occur as a result of what hypersensitivity type?

Answer 32

Type 3 - Immune complex

Question 33

What should you worry about on seeing a corneal melt?

Answer 33

possibility of eye perforation

Question 34

Give an example of a Type IV hypersensitivity reaction

Answer 34

corneal graft rejection

Question 35

How can you tell that a corneal graft is being rejected by its host?

Answer 35

Vascularisation (blood vessels) of host cornea are growing and almost reaching the donor tissue

Question 36

What ocular side effects do steroids induce?

Answer 36

Cataracts

Steroid-induced glaucoma

Question 37

Graft rejection can be saved if acted on quickly. TRUE/FALSE?

Answer 37

TRUE