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Ophthalmology > Immunology and the eye > Flashcards

Immunology and the eye Flashcards

1
Q

What is included in the innate immune system of the eye?

A

No physical barrier
Not many commensals
Chemical agents
Cell

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2
Q

How does the eye protect itself?

A

Blink reflex
Physical and chemical properties of eye surface
Limit exposure

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3
Q

How does the blink reflex protect the eye?

A

Physical tears
Flushing
Mucous layer

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4
Q

What is present in tears that allows them to act as a chemical barrier?

A

Lysozyme: protects against gram negative bacteria and fungi
Lactoferrin and transferrin: protective against gram positive bacteria
Tear lipids: antibacterial to cell membranes/ scavenger of bacterial products
Angiogenin: antimicrobial effect within tear film
Secretory IgA: prevents attachment
Complement
IL-6, IL-8, MIP: antimicrobial molecules that recruit leukocytes

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5
Q

What cells are present in tears that help them to act as a barrier?

A

Neutrophils: chemotaxic, scavengers
Macrophages: phagocytosis of damaged cells, helps to trigger adaptive immune system
Conjunctival mast cells: vasoactive mediators

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6
Q

What does the adaptive immune system require?

A

Antigen presenting cells - dendritic cells, B cells, macrophages
Lymphatic drainage to lymph nodes
Variety of effector cells (CD4+ T cells, CD8+ T cells, B cells)

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7
Q

What is the role of langerhans cells in the eye?

A 
Principle APC for external eye
Rich in class 2 MHC molecules
Found at limbus
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8
Q

What immunological features can be found at the conjunctiva?

A

Only part with lymph drainage
Specialised endothelial venules for regulated migration of lymphoid cells
Diffuse lymphoid populations in all conjunctival zones (CD4+ CD8+ T cells, IgA plasma cells)
Dendritic cells as APC
MALT
Commensal bacteria

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9
Q

What immunological features can be found at the cornea and sclera?

A 
Tough collagen coat
Avascular
No lymphatics
Lack of APC
Langerhans cells only in peripheral cornea
Down Regulated immune environment
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10
Q

What is the role of the lacrimal gland in immune protection of eye?

A 
More plasma (IgA) cells and CD8+ T cells than conjunctiva
T cells in small groups around intralobular ducts
Resting lymphoid cells very rarely observed
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11
Q

What is the role of the lacrimal drainage system in immune protection of the eye?

A

Diffuse lymphoid tissue and follicles in MALT

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12
Q

What are immune privilege sites in the body?

A

Brain/CNS
Testes
Placenta/ foetus
Eye

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13
Q

What sites in the eye are immune privileged?

A 
Cornea
Anterior chamber
Lens
Vitreous cavity
Subretinal space
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14
Q

What is immune privilege?

A

Tolerate introduction of antigens without eliciting an inflammatory response

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15
Q

How does the eye have immune privilege?

A

Blood-tissue barrier with a lack of lymph drainage
Ocular microenvironment is rich in immunosuppressive molecules and inhibitor cell surface molecules that influence the reactivity of immune cells
Anterior chamber associated immune deviation

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16
Q

What is anterior chamber associated immune deviation (ACAID)?

A

Placement of foreign antigen into the ocular microenvironment can induce a systemic form of tolerance to the foreign antigen
Downregulates immune response within the eye

17
Q

What are the hallmarks of ACAID?

A

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

18
Q

What is the purpose of ACAID?

A

Protects eye and visual axis from the collateral damage of an immune response to infection by suppressing a future potentially damaging response to infection

19
Q

How is ocular immune privilege established?

A

SeparationL immunological ignorance; corneal cells have a decreased expression of MHC class 1 molecules and do not express MHC class 2 molecules
Normal cornea lacks blood and lymph
Inhibition: development of an intraocular immunosuppressive microenvironemt
Regulation: ACAID

20
Q

What is sympathetic ophthalmia?

A

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

21
Q

What immunological cells determine sympathetic ophthalmia?

A

Primary mediators are T cells
Initial wave of infiltrative cells composed of CD4+ helper T cells
Later wave of infiltrative cells at CD8+ cytotoxic T cells

22
Q

What are hazards of immunity?

A 
Recurrent infections
Inadvertent injury to normal host tissue
Allergy
Hypersensitivity reactions
Autoimmune disease
Cancer
Transplant/ graft rejection
23
Q

What autoimmune diseases can affect the eye?

A 
Autoimmune uveoretinitis
Dalen-fuchs nodule
Keratoconjunctivitis sicca
Lens-induced uveitis 
Retina autoantibodies
Sympathetic ophthalmia
24
Q

Hypersensitivity reactions?

A

Type 1: immediate hypersensitivity
Type 2: direct cell killing
Type 3: immune complex mediated
Type 4: delayed type hypersensitivity

25
Q

What are examples of ocular type 1 hypersensitivity reactions?

A

Acute allergic conjunctivitis with associated chemosis

26
Q

What is chemosis?

A

Oedema of the conjunctiva

27
Q

What mediated type 2 hypersensitivity?

A

Macrophages/ NK cells

Complement (MAC)

28
Q

What is an example of ocular type 2 hypersensitivity reactions?

A

Ocular cicatricial pemphigoid

Blistering and scarring of conjunctiva

29
Q

What is an example of ocular type 3 hypersensitivity reactions?

A

Autoimmune corneal melting: outer layer of corneal melting, inner layer bulging forward; possible perforation

30
Q

What is an example of type 4 hypersensitivity reaction in the eye?

A

Corneal graft rejection - vascularisation of host cornea reaching donor tissue

31
Q

What ocular side effects can occur with steroids?

A

Cataracts

Steroid-induced glaucoma

Ophthalmology (14 decks)

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