Physiology: Immunology and the Eye

Question 1

What is the immunological function of the blink reflex?

Answer 1

Tears flush the surface of the eye

Question 2

What is the immunological function of the mucous layer of the eye?

Answer 2

Acts as an anti-adhesive

Question 3

Name two antimicrobial agents found within tears

Answer 3

Lysozyme, secretory IgA

Question 4

Name the immune cells found in tears

Answer 4

Neutrophils, macrophages and conjunctival mast cells

Question 5

Name the principle antigen presenting cell (macrophage) for external eye

Answer 5

Langerhans cells

Question 6

Where is the concentration of Langerhans cells highest?

Answer 6

Corneo-scleral limbus

Question 7

Langerhans cells are rich in class ___ MHC molecules

Answer 7

II

Question 8

Name the only part of the eye with lymphatic drainage

Answer 8

Conjunctiva

Question 9

Name immune cells always present in the MALT of the conjunctiva

Answer 9

Macrophages, Langerhans cells and mast cells

Question 10

Name the immune cells found in the cornea and sclera

Answer 10

No lymphatics/lymphoid tissue, relative lack of APCs, Langerhans cells only in peripheral cornea

Question 11

Name the immune cells found in the lacrimal gland

Answer 11

More plasma cells (IgA) and CD8+ T cells compared to conjunctiva

T cells in small groups around intralobar duct

Resting lymphoid cells rarely observed

Question 12

Where is MALT found in the eye?

Answer 12

Conjunctiva, lacrimal drainage

Question 13

What is the blood-ocular barrier?

Answer 13

Barrier created by endothelium of capillaries of the retina and iris, ciliary epithelium and retinal pigment epithelium

Question 14

What is immune privilege?

Answer 14

Certain sites of the human body, including in the eyes, have immune privilege; they are able to tolerate the introduction of antigens without eliciting an inflammatory response

Question 15

Name the areas in the eye which have immune privilege

Answer 15

Cornea, anterior chamber, lens, vitreous cavity, subretinal space

Question 16

Name three mechanisms by which the eye achieves immune privilege

Answer 16

1. Anatomical, cellular, and molecular barriers in the eye (blood-ocular barrier, lack of lymphatic drainage)
2. Eye-derived immunological tolerance - anterior chamber-associated immune deviation (ACAID)
3. Immune suppressive intraocular microenvironment

Question 17

What is sympathetic ophthalmia?

Answer 17

Rare, bilateral granulomatous uveitis due to trauma (more common) or surgery (less common) to one eye

Question 18

Describe the pathophysiology of sympathetic ophthalmia

Answer 18

Thought to be secondary to development of an autoimmune reaction to ocular antigens which are exposed during the traumatic or surgical event - disadvantage of immune privilege in the eye

Question 19

Which immune cells are believed to be the primary mediators for sympathetic ophthalmia?

Answer 19

T cells

Question 20

How would you distinguish between the ‘exciting eye’ and the ‘sympathising eye’ in sympathetic ophthalmia?

Answer 20

Clinically both eyes appear the same - can only tell by the history

Question 21

Which type of hypersensitivity is described as immediate and IgE mediated?

Answer 21

Type I

Question 22

Which type of hypersensitivity involves direct cell killing (by macrophages/NK cells or complement + MAC)?

Answer 22

Type II

Question 23

Which type of hypersensitivity is immune complex mediated?

Answer 23

Type III

Question 24

Which type of hypersensitivity involves cell-mediated cytotoxicity?

Answer 24

Type IV

Question 25

Give an ocular example of a type I hypersensitivity reaction

Answer 25

Acute allergic conjunctivitis +/- chemosis

Question 26

Give an ocular example of a type II hypersensitivity reaction

Answer 26

Ocular cicatricial pemphigoid

Question 27

What is ocular cicatricial pemphigoid?

Answer 27

Type of autoimmune conjunctivitis involving blistering and scarring of conjunctiva

Question 28

Give an ocular example of a type III hypersensitivity reaction

Answer 28

Autoimmune corneal melting

Question 29

Give an ocular example of a type IV hypersensitivity reaction

Answer 29

Corneal graft rejection

Question 30

What causes corneal graft rejection?

Answer 30

Type IV hypersensitivity due to vascularisation of host cornea

Question 31

Name two ocular side effects of steroids

Answer 31

Cataracts and steroid-induced glaucoma

Question 32

List 3 factors that help to maintain immune privilege in corneal transplants

Answer 32

1. Lack of immune cells (MHC molecules, Langerhans)
2. Immunosuppressive molecules and inhibitory surface molecules
3. Cornea lacks blood and lymph