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2 Ophthalmology > Immunology of the Eye > Flashcards

Immunology of the Eye Flashcards

1
Q

what is the innate immune system

A

first line defence - rapid response (mins-hours)
physical barrier

targets groups of pathogens
no memory
targets a limited number of bacterial structures

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2
Q

what is the adaptive immune system

A

acquired, learned, specific immunity

takes days

has memory -allows you to build tolerance to pathogen if you encounter it again

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3
Q

what are the innate immune features of the eye

A

chemical agents and immune cells

no skin barrier and few commensals

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4
Q

how does the eye protect itself (first line)

A

blink reflex - tears
Lysozyme on the eye surface (plus lots of other anti-bacterial properties)
Limit exposure/size

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5
Q

what layers does the tear film have

A

lipid layer
aqueous layer
mucin layer - anti-adhesive

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6
Q

what anti-microbial properties do the tears have

A 
lysozyme (destroys cell walls) 
lactoferrin and transferrin 
antibacterial lipids 
angiogenin 
IgA 
complement 
IL6, IL8, MIP
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7
Q

what immune cells are in the tears

A

neutrophils
macrophages
conjunctival cells

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8
Q

what does the adaptive immune system require to work

A
  1. Antigen presenting cells
  2. lymphatic drainage to lymph nodes
  3. variety of effector cells (CD4+, CD8+ T cells, B cells)
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9
Q

what are the principle APCs for the external eye

A

Langerhans cells (rich in class II MHC molecules)

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10
Q

where are most langerhans cells found

A

at the cornea-scleral limbus - less in the peripheral cornea and ABSENT in the central 1/3 of the cornea

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11
Q

what part of the eye is the only part with lymphatic drainage

A

conjunctiva

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12
Q

what immune features are found in conjunctival zones

A 
dendritic cells 
mucosa associated lymphoid tissue 
macrophages 
langerhans cells 
mast cells 
commensal bacteria
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13
Q

are the cornea and sclera avascular/vascular

A

avascular

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14
Q

what section of the cornea contains langerhans cells

A

peripheral cornea

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15
Q

the sclera and cornea have a normal immune environment true/false

A

false

a down regulated immune environment

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16
Q

what immune features are seen in the lacrimal gland

A 
plasma cells (IgA) 
CD8+ T cells
17
Q

what protects the vitreous compartment, choroid and retina from infection

A

blood-ocular barrier
Lack of APCs
Down regulated immune environment (to prevent collateral damage from immune responses)

18
Q

why is the immune environment in the eye down regulated

A

because there is potential for a lot of collateral damage from inflammation

19
Q

What is immune privilege

A

an active process where parts of the body are able to tolerate the introduction of antigens without eliciting an inflammatory immune response

20
Q

what sites in the eye are immune-privileged

A 
cornea 
anterior chamber 
lens 
vitreous cavity 
sub retinal space
21
Q

how is ocular immune privilege established

A

separation: cornea is separated from immune system by lack of blood and lymphatic vessels
inhibition: development of an intraocular immunosuppressive environment
regulation: peripheral tolerance to ocular antigens (ACAID)

22
Q

what is anterior chamber associated immune deviation (ACAID)

A

if a pathogen gets into the anterior chamber, peripheral tolerance to the antigen occurs

  • suppressed a future potentially damaging response to infection
23
Q

what is sympathetic ophthalmia

A

rare bilateral granulomatous uveitis due to trauma or surgery to 1 eye

(secondary development of autoimmune reaction to ocular antigens exposed during trauma)

Disadvantage of immune privilege - related to the immune isolation of the eye

24
Q

what are the primary mediators in sympathetic ophthalmia

A

T cells

25
Q

what is the injured eye called in sympathetic ophthalmia

A

exciting eye

other eye is the sympathising eye- can only tell the difference from history

26
Q

what are some side effects of a defective/absent immune system

A 
recurrent (severe) infections 
ignores innocuous substances 
tolerance to self 
acceptance of transplanted organs/tissues 
cancer
27
Q

what are the side effects of a hyperactive immune system

A

protection from harmful pathogens

responds to innocuous substances

responds to self

rejection of transplanted organs/tissues

28
Q

what is a type 1 hypersensitivity reaction

A

ALLERGIC RESPONSE

B cells encounter allergens so produces IgE - clears allergen

mast cells bind to the left over IgE which wasn’t cleared

this means next time the pathogen is encountered, because the IgE is already attach to the mast cells it immediately reacts to the pathogen

mast cells release loads of inflammatory mediators

29
Q

what is an example of a type 1 hypersensitivity reaction in the eye

A

acute allergic conjunctivitis

30
Q

what is a type 2 hypersensitivity reaction

A

direct killing/antibody response

The pathogen is killed by either Macrophages/NK cells or complement

31
Q

what is an example of a type 2 hypersensitivity reaction in the eye

A

ocular cicatrical pemphigoid

type of autoimmune conjunctivitis: blistering and scarring of the conjunctiva

32
Q

what is type 3 hypersensitivity

A

Immune complex mediated

Immune system produces too much antibody and the complexes can’t get cleared leading to inflammation

33
Q

example of type 3 hypersensitivity in the eye

A

Autoimmune corneal melting

34
Q

what is type 4 hypersensitivity

A

delayed type

complex reactions which take a long time to come about but are v adapted

clonal expansion of T cells lead to an exaggerated immune response

35
Q

example of type 4 hypersensitivity reactions in the eye

A

corneal graft rejection

36
Q

what factors in the eye help maintain immune privilege

A

reduced and impaired expression of MHC I and II molecules in cornea

cornea lacks blood and lymph vessels

Central cornea is deficient in lagerhands

secretion of molecules with immunosuppressive properties inhibits immune cells

expression of surface molecules to inhibit immune effectors

ACAID in the peripheral immune system

37
Q

side effects of steroids in the eye

A

cataracts

steroid-induced glaucoma

2 Ophthalmology (16 decks)

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