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Ophthalmology > Immunology > Flashcards

Immunology Flashcards

1
Q

innate immunological barriers that are not present in the eye

A
  • no physical barrier as no skin

- not many commensal bacteria

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2
Q

solutions to the lack of physical barrier in the eye

A

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

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3
Q

physical barrier of tears

A

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

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4
Q

chemical barrier of tears

A 
lysozymes
lactoferrin
lipids
angiogenin
sIgA
complement
IL-6
IL-8
MIP
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5
Q

cellular barrier of tears

A

neutrophils
macrophages
conjunctival mast cells

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6
Q

adaptive immune system in the eye

A

langerhans cells (APC)

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7
Q

where are Langerhans cells abundant?

A

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

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8
Q

immunological properties of conjunctiva

A
  • 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
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9
Q

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

A

yes

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10
Q

cornea and sclera immunological properties

A
  • tough collagen is avascular with no lymphatics

- langerhans in peripheral cornea and corneo-scleral limbus

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11
Q

describe the lacrimal gland and drainage system immunological properties

A
  • lacrimal gland has plasma cells e.g. IgA and CD8+ T cells (intralobar ducts)
  • drainage contains diffuse lymphoid tissue and follicles in mucosa MALT
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12
Q

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

A

yes

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13
Q

describe immunological properties of vitreous, choroid and retina?

A

blood-ocular barrier

lack of APCs

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14
Q

what is immune privilege?

A

able to tolerate antigens without eliciting an inflammatory immune response

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15
Q

how is the eye able to have immune privilege?

A
  • blood-tissue barrier
  • lack of lymphatic drainage
  • rich in immunosuppressive cells and inhibitory surface molecules
  • ACAID
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16
Q

what does ACAID stand for?

A

anterior chamber-associated immune deviation

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17
Q

what is ACAID

A

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

18
Q

why does the eye have immune privilege?

A

protects it from collateral damage from an immune response

19
Q

three ways the establishment of ocular immune privilege occurs

A
  1. separation: reduced MHC, cornea lacks blood and lymphatic vessels
  2. inhibition: inhibitory components
  3. regulation: ACAID
20
Q

define sympathetic opthalmia

A

bilateral granulomatous uveitis

21
Q

cause of sympathetic opthalmia

A

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

22
Q

causative event of sympathetic opthalmia

A

trauma

surgery

23
Q

example of a disadvantage of immune privilege

A

sympathetic ophthalmia

24
Q

in sympathetic ophthalmia what is the injured eye called?

A

exciting eye

25
Q

in sympathetic ophthalmia what is the uninjured eye called?

A

sympathising eye

26
Q

describe how sympathetic ophthalmia occurs?

A
  • 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)
27
Q

examples of ocular AI diseases

A
  • 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.
28
Q

define hypersensitivity reaction

A

immune response that results in bystander damage to self

29
Q

what is the classification system used for hypersensitivity?

A

Gel and Coomb’s

30
Q

describe type 1 (immediate hypersensitivity)

A
  • 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
31
Q

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

A

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

32
Q

examples of direct cell killing (type 2) condition

A

ocular cicatricial pemphigoid

33
Q

presentation of ocular cicatricial pemphigoid

A

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

34
Q

management of ocular cicatricial pemphigoid

A

steroids

35
Q

describe type 3 (immune complex mediated)

A

antigen-antibody complexes are formed and deposited in various tissues

36
Q

example of type 3 condition

A

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

37
Q

management of type 3 (AI corneal melting)

A

steroids

38
Q

describe type 4 (delayed/ cell-mediated cytotoxicity)

A

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

39
Q

example of type 4 condition

A

corneal graft rejection (rare due to immune privilege)

there is vascularisation of host cornea reaching donor tissue

40
Q

factors that maintain immune privilege

A
  • 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)
41
Q

ocular side effects of steroids

A

cataracts

steroid-induced glaucoma

Ophthalmology (28 decks)

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