Immunology

Question 1

innate immunological barriers that are not present in the eye

Answer 1

• no physical barrier as no skin

- not many commensal bacteria

Question 2

solutions to the lack of physical barrier in the eye

Answer 2

blink reflex
physical and chemical agents
limiting exposure e.g. eye sits back in the head

Question 3

physical barrier of tears

Answer 3

tears are flushed across the eye when blinking

cornea contains a mucous layer that is anti-adhesive preventing microorganisms and dirt from sticking to the eye

Question 4

chemical barrier of tears

Answer 4

lysozymes
lactoferrin
lipids
angiogenin
sIgA
complement
IL-6
IL-8
MIP

Question 5

cellular barrier of tears

Answer 5

neutrophils
macrophages
conjunctival mast cells

Question 6

adaptive immune system in the eye

Answer 6

langerhans cells (APC)

Question 7

where are Langerhans cells abundant?

Answer 7

corneo-scleral limbus with less in peripheral cornea and absent from central 1/3rd

Question 8

immunological properties of conjunctiva

Answer 8

• only part with lymphatic drainage
• endothelial venules (regulate migration of immune cells)
• diffuse effector cells in conjunctival zones (T and B cells)
• MALT (mucosa associated lymphoid tissue) contains macrophages, Langerhans and mast cells
• commensal bacteria

Question 9

is the cornea and sclera a downregulated immunological layer of the eye?

Answer 9

yes

Question 10

cornea and sclera immunological properties

Answer 10

• tough collagen is avascular with no lymphatics

- langerhans in peripheral cornea and corneo-scleral limbus

Question 11

describe the lacrimal gland and drainage system immunological properties

Answer 11

• lacrimal gland has plasma cells e.g. IgA and CD8+ T cells (intralobar ducts)
• drainage contains diffuse lymphoid tissue and follicles in mucosa MALT

Question 12

is the vitreous, choroid and retina a downregulated immunological part of the eye?

Answer 12

yes

Question 13

describe immunological properties of vitreous, choroid and retina?

Answer 13

blood-ocular barrier

lack of APCs

Question 14

what is immune privilege?

Answer 14

able to tolerate antigens without eliciting an inflammatory immune response

Question 15

how is the eye able to have immune privilege?

Answer 15

• blood-tissue barrier
• lack of lymphatic drainage
• rich in immunosuppressive cells and inhibitory surface molecules
• ACAID

Question 16

what does ACAID stand for?

Answer 16

anterior chamber-associated immune deviation

Question 17

what is ACAID

Answer 17

placement of foreign antigen into the ocular environment induces a systemic tolerance to the foreign antigen

Question 18

why does the eye have immune privilege?

Answer 18

protects it from collateral damage from an immune response

Question 19

three ways the establishment of ocular immune privilege occurs

Answer 19

1. separation: reduced MHC, cornea lacks blood and lymphatic vessels
2. inhibition: inhibitory components
3. regulation: ACAID

Question 20

define sympathetic opthalmia

Answer 20

bilateral granulomatous uveitis

Question 21

cause of sympathetic opthalmia

Answer 21

development of an AI reaction due to ocular antigens expose during the causative event

Question 22

causative event of sympathetic opthalmia

Answer 22

trauma

surgery

Question 23

example of a disadvantage of immune privilege

Answer 23

sympathetic ophthalmia

Question 24

in sympathetic ophthalmia what is the injured eye called?

Answer 24

exciting eye

Question 25

in sympathetic ophthalmia what is the uninjured eye called?

Answer 25

sympathising eye

Question 26

describe how sympathetic ophthalmia occurs?

Answer 26

- trauma in one eye results in release of intraocular antigens - carried to lymph nodes and activate T cells - T cells return in bloodstream and encounter antigen in both eyes (lack of specificity)

Question 27

examples of ocular AI diseases

Answer 27

- Autoimmune uveoretinitis= inflammation of the uvea and retina - Dalen-Fuchs nodule= epithelial cell clusters in retinal layers - Keratoconjunctivitis sicca (dry eyes) - Lens-induced uveitis= reaction to release of lens products - Retina autoantibodies= common in retinopathy associated with cancer/infection/ degenerative disease - Sympathetic ophthalmia= bilateral granulomatous uveitis.

Question 28

define hypersensitivity reaction

Answer 28

immune response that results in bystander damage to self

Question 29

what is the classification system used for hypersensitivity?

Answer 29

Gel and Coomb's

Question 30

describe type 1 (immediate hypersensitivity)

Answer 30

- encountering an antigen B cells produce IgE which targets the pathogen and its cleared - excess IgE is produced and so binds to Fc receptors on mast cells - upon re-encounter B cells are not needed as there is excess IgE - mast cells release IgE and there own vasoactive substances e.g. histamine

Question 31

describe type 2 (direct cell killing/ antibody-mediated cytotoxicity)

Answer 31

cells are killed by NK cells (macrophages) or complement (MAC)

Question 32

examples of direct cell killing (type 2) condition

Answer 32

ocular cicatricial pemphigoid

Question 33

presentation of ocular cicatricial pemphigoid

Answer 33

blisters on eyelids and eye surface healing leads to scarring and adhesions lid can be held open

Question 34

management of ocular cicatricial pemphigoid

Answer 34

steroids

Question 35

describe type 3 (immune complex mediated)

Answer 35

antigen-antibody complexes are formed and deposited in various tissues

Question 36

example of type 3 condition

Answer 36

AI corneal melting (inner layer bulges forward so can risk perforation)

Question 37

management of type 3 (AI corneal melting)

Answer 37

steroids

Question 38

describe type 4 (delayed/ cell-mediated cytotoxicity)

Answer 38

T cells are activated by intracellular pathogens and undergo clonal expansion re-exposure produces an exaggerated immune response

Question 39

example of type 4 condition

Answer 39

corneal graft rejection (rare due to immune privilege) | there is vascularisation of host cornea reaching donor tissue

Question 40

factors that maintain immune privilege

Answer 40

- reduced MHC I and II - cornea lacks blood and lymph vessels - central cornea lacks Langerhans (lengthens time for graft recognition) - secretion of immunosuppressive cells and expansion of surface molecules inhibiting immune effectors (ACAID in recipients)

Question 41

ocular side effects of steroids

Answer 41

cataracts | steroid-induced glaucoma