Immunology and the Eye

Question 1

What is the role of lysozyme on the eye surface?

Answer 1

Active against gram -ve bacteria, fungi (destroy bacteria cell wall)

Question 2

What is the role of lactoferrin and transferrin on the eye surface?

Answer 2

Active against gram +ve bacteria

Question 3

What is the role of tear lipids on the eye surface?

Answer 3

Antibacterial to cell membranes/scavenger of bacterial products

Question 4

What is the role of angiogenin on the eye surface?

Answer 4

Antibacterial to cell membranes/scavenger of bacterial products

Question 5

What is the role of secretory IgA on the eye surface?

Answer 5

Prevents attachment

Question 6

What is the role of IL-6, IL-7 and MIP on the eye surface?

Answer 6

Antimicrobial molecules that recruit leucocytes

Question 7

What is the role of neutrophils in the eye?

Answer 7

Scavengers- release free radicals and enzymes

Question 8

What is the role of macrophages in the eye?

Answer 8

Phagocytosis of damaged cells

Help to trigger adaptive immune system

Question 9

What is the role of conjunctival mast cells in the eye?

Answer 9

Vasoactive mediators

Question 10

What are the three components of the adaptive immune system

Answer 10

1) Antigen presenting cells (APC= dendritic cells, B cells, macrophages)
2) Lymphatic drainage to lymph node
3) Variety of effector cells (incl CD4+T Cells, CD8 + T Cells, B Cells)

Question 11

What is the role of langerhans cells in the eye?

Answer 11

Principle APC for external eye

Rich in class II MHC molecules

Question 12

Where are langerhans cells present?

Answer 12

Abundant in corneo-scleral limbus

Less in peripheral cornea

Absent from 1/3rd of conjunctiva

Question 13

Which part of the eye has lymphatic drainage?

Answer 13

Conjunctiva

Question 14

What does the conjunctiva contain to allow lymphatic drainage?

Answer 14

Specialised endothelial venues for regulated migration of lymphoid cells

Question 15

What lymphoid populations are found in the conjunctiva?

Answer 15

CD4+T cells, CD8+T cells, IgA secreting plasma cells

Question 16

What cells frequent the conjunctiva (MALT) of the eye?

Answer 16

Macrophages, langerhans cells and mast cells

Neutrophils only if recruited

Commensal bacteria

Question 17

Describe the structure of the cornea and sclera

Answer 17

Tough collagen coat

Avascular

No lymphatics/lymphoid tissue

Question 18

Describe the immune presence of the cornea and sclera

Answer 18

Lack of APCs

Langerhans only in peripheral cornea

Down-regulated environment

Question 19

Which immune cells are found in the lacrimal gland?

Answer 19

Plasma IgA cells, CD8+T cells

Question 20

What cells are found around intralobar ducts in the lacrimal gland?

Answer 20

T cells in small groups

Question 21

What is rarely observed in the lacrimal gland?

Answer 21

Resting lymphoid cells

Question 22

What provides the drainage of the lacrimal gland?

Answer 22

Diffuse lymphoid tissue and follicles (40-50%)

Question 23

Describe the immune environment of the vitreous, choroid and retina

Answer 23

Blood-ocular barrier

Relative lack of APCs

Downregulated immune environment

Question 24

Which parts of the body have immune privilege?

Answer 24

Brain/CNS
testes
Placenta/foetus
Eyes

Question 25

What is immune privilege?

Answer 25

Able to tolerate the introduction of antigens without eliciting an inflammatory response

Question 26

Which sites in the eye have immune privilege?

Answer 26

``` Cornea Anterior chamber Lens Vitreous Cavity Sub retinal space ```

Question 27

What is ACAID?

Answer 27

Anterior Chamber Associated Immune Deviation Protects eye and visual axis from collateral damage of an immune response to infection by suppressing a future response

Question 28

What are the immunological hallmarks of ACAID?

Answer 28

Generation of primed CD4+T and B cells that produce non-complement-fixing antibodies Inhibition of delayed-type hypersensitivity (CD4+ Th1 and B cells) that secrete complement-fixing antibodies

Question 29

Describe Separation (Immunological ignorance)

Answer 29

Corneal cells have reduced expression of MHC I molecules and do not express MHC II molecules Normal cornea lacks blood and lymphatic vessels

Question 30

Describe inhibition (development of an intracular immunosuppressive microenvironment)

Answer 30

Local factors within the eye inhibit components of the immune system to reinforce protection of immune privilege

Question 31

Describe regulation (peripheral tolerance to ocular antigen)

Answer 31

ACAID

Question 32

What is sympathetic ophthalmia?

Answer 32

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

Question 33

What are the primary mediators of sympathetic ophthalmia?

Answer 33

T cells

Question 34

What is the initial infiltrative wave in sympathetic ophthalmia?

Answer 34

CD4+ helper T cells

Question 35

What is the later infiltrative wave in sympathetic ophthalmia?

Answer 35

CD8 + cytotoxic T cells

Question 36

What are the injured and fellow eye known as in sympathetic ophthalmia?

Answer 36

Injured=exciting eye Fellow= sympathising eye

Question 37

What are the hazards of immunity in the eye?

Answer 37

Recurrent Infection Inadvertent injury to normal host tissues Allergy Hypersensitivity reactions Autoimmune disease CAncer Transplant/graft rejection

Question 38

What is autoimmune uveoretinitis?

Answer 38

Inflammation of the uvea and retina

Question 39

What is a dalen-fuchs nodule?

Answer 39

epithelial cells cluster in retinal layers

Question 40

What is keratoconjunctivitis sicca?

Answer 40

Dry eyes

Question 41

Describe mast cells in type 1 immediate hypersensitivity reactions

Answer 41

Mast cells express receptors for Fc region of IgE antibody on surface, when encounter allergen, B cells produce antigen-specific IgE antibody

Question 42

What happens on re-encounter with antigen in type 1 reactions?

Answer 42

residual IgE antibodies bind to circulating mast cells via Fc receptors on re-encounter with antigen allergen binds to IgE coated mast cells and disrupts cell membrane release of vasoactive mediators- histamine, tryptase etc also increased cytokines and leukotriene transcription

Question 43

Give an example of a type 1 immune reaction in the eye

Answer 43

acute allergic conjunctivitis, | causes chemosis= oedema of the conjunctiva

Question 44

What are the killing cells in type 2 immune reactions?

Answer 44

Macrophages/NK cells | Complement (MAC)

Question 45

Give an example of Type 2 immune reaction in the eye

Answer 45

Ocular cicatricial pemphigoid utoimmune conjunctivitis: blistering and scarring of the conjunctiva

Question 46

What are type 3 immune reactions mediated by?

Answer 46

Formation of antigen-antibody complexes

Question 47

Give an example of Type 3 immune reaction in the eye

Answer 47

autoimmune corneal melting, outer layer of cornea melting: inner layer bulging forward, possible perforation

Question 48

Describe type 4 autoimmune reactions

Answer 48

T helper cells activated by intracellular pathogens clonal expansion when re-exposed, macrophages attracted exaggerated immune response

Question 49

Give an example of a type 4 immune reaction in the eye?

Answer 49

Corneal graft rejection

Question 50

Which diseases- thought to be age related- are now thought to have an immune component?

Answer 50

adult macular degeneration (AMD), glaucoma, diabetic retinopathy

Question 51

What is the proposed aetiology of immunity in age related diseases?

Answer 51

ocular immune priviledge combined with a lack of age-related antigens within the target tissue dampen what could otherwise be overt inflammation into the para-inflammation (slow, insidious) that characterises age-related neurodegenerative disease