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Ophthalmology > Immunology and the Eye > Flashcards

Immunology and the Eye Flashcards

1
Q

What is the role of lysozyme on the eye surface?

A

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

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2
Q

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

A

Active against gram +ve bacteria

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3
Q

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

A

Antibacterial to cell membranes/scavenger of bacterial products

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4
Q

What is the role of angiogenin on the eye surface?

A

Antibacterial to cell membranes/scavenger of bacterial products

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5
Q

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

A

Prevents attachment

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6
Q

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

A

Antimicrobial molecules that recruit leucocytes

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7
Q

What is the role of neutrophils in the eye?

A

Scavengers- release free radicals and enzymes

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8
Q

What is the role of macrophages in the eye?

A

Phagocytosis of damaged cells

Help to trigger adaptive immune system

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9
Q

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

A

Vasoactive mediators

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10
Q

What are the three components of the adaptive immune system

A

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)

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11
Q

What is the role of langerhans cells in the eye?

A

Principle APC for external eye

Rich in class II MHC molecules

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12
Q

Where are langerhans cells present?

A

Abundant in corneo-scleral limbus

Less in peripheral cornea

Absent from 1/3rd of conjunctiva

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13
Q

Which part of the eye has lymphatic drainage?

A

Conjunctiva

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14
Q

What does the conjunctiva contain to allow lymphatic drainage?

A

Specialised endothelial venues for regulated migration of lymphoid cells

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15
Q

What lymphoid populations are found in the conjunctiva?

A

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

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16
Q

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

A

Macrophages, langerhans cells and mast cells

Neutrophils only if recruited

Commensal bacteria

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17
Q

Describe the structure of the cornea and sclera

A

Tough collagen coat

Avascular

No lymphatics/lymphoid tissue

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18
Q

Describe the immune presence of the cornea and sclera

A

Lack of APCs

Langerhans only in peripheral cornea

Down-regulated environment

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19
Q

Which immune cells are found in the lacrimal gland?

A

Plasma IgA cells, CD8+T cells

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20
Q

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

A

T cells in small groups

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21
Q

What is rarely observed in the lacrimal gland?

A

Resting lymphoid cells

22
Q

What provides the drainage of the lacrimal gland?

A

Diffuse lymphoid tissue and follicles (40-50%)

23
Q

Describe the immune environment of the vitreous, choroid and retina

A

Blood-ocular barrier

Relative lack of APCs

Downregulated immune environment

24
Q

Which parts of the body have immune privilege?

A

Brain/CNS
testes
Placenta/foetus
Eyes

25
Q

What is immune privilege?

A

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

26
Q

Which sites in the eye have immune privilege?

A 
Cornea
Anterior chamber
Lens
Vitreous Cavity 
Sub retinal space
27
Q

What is ACAID?

A

Anterior Chamber Associated Immune Deviation

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

28
Q

What are the immunological hallmarks of ACAID?

A

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

29
Q

Describe Separation (Immunological ignorance)

A

Corneal cells have reduced expression of MHC I molecules and do not express MHC II molecules

Normal cornea lacks blood and lymphatic vessels

30
Q

Describe inhibition (development of an intracular immunosuppressive microenvironment)

A

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

31
Q

Describe regulation (peripheral tolerance to ocular antigen)

A

ACAID

32
Q

What is sympathetic ophthalmia?

A

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

33
Q

What are the primary mediators of sympathetic ophthalmia?

A

T cells

34
Q

What is the initial infiltrative wave in sympathetic ophthalmia?

A

CD4+ helper T cells

35
Q

What is the later infiltrative wave in sympathetic ophthalmia?

A

CD8 + cytotoxic T cells

36
Q

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

A

Injured=exciting eye

Fellow= sympathising eye

37
Q

What are the hazards of immunity in the eye?

A

Recurrent Infection

Inadvertent injury to normal host tissues

Allergy

Hypersensitivity reactions

Autoimmune disease

CAncer

Transplant/graft rejection

38
Q

What is autoimmune uveoretinitis?

A

Inflammation of the uvea and retina

39
Q

What is a dalen-fuchs nodule?

A

epithelial cells cluster in retinal layers

40
Q

What is keratoconjunctivitis sicca?

A

Dry eyes

41
Q

Describe mast cells in type 1 immediate hypersensitivity reactions

A

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

42
Q

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

A

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

43
Q

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

A

acute allergic conjunctivitis,

causes chemosis= oedema of the conjunctiva

44
Q

What are the killing cells in type 2 immune reactions?

A

Macrophages/NK cells

Complement (MAC)

45
Q

Give an example of Type 2 immune reaction in the eye

A

Ocular cicatricial pemphigoid

utoimmune conjunctivitis: blistering and scarring of the conjunctiva

46
Q

What are type 3 immune reactions mediated by?

A

Formation of antigen-antibody complexes

47
Q

Give an example of Type 3 immune reaction in the eye

A

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

48
Q

Describe type 4 autoimmune reactions

A

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

49
Q

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

A

Corneal graft rejection

50
Q

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

A

adult macular degeneration (AMD), glaucoma, diabetic retinopathy

51
Q

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

A

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

Ophthalmology (15 decks)

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