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Y2 Opthalmology > Immunology > Flashcards

Immunology Flashcards

1
Q

What aspects of eye physiology contribute to the barrier aspect of the innate immune system?

A

Blink reflex
Physical and chemical properties of eye surface
Limited exposure/size

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2
Q

How do tears physically aid the innate immune system?

A

Flushing of the eye

Mucous layer anti-adhesive

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3
Q

How do tears chemically aid the innate immune system?

A

Lysozyme (vs gram -ve and fungi)
Lactoferrin and transferrin (vs gram +ve)
Tear lipids (antimicrobial to membranes, scavenger of bacterial products)
Angiogenin (antimicrobial)
Secretory IgA (prevents attachment)
Complement
IL-6, IL-8 and MIP (antimicrobial, recruit leucocytes)

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4
Q

What immune cells in the eye are part of the innate immune system?

A

Neutrophils
Macrophages
Conjunctival Mast Cells

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5
Q

What are the 3 main requirement of the adaptive immune system?

A
  1. Antigen presenting cells
  2. Lymphatic drainage
  3. Effector cells
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6
Q

What are the APCs in the adaptive immune system of the eye?

A

Dendritic cells
B cells
Macrophages

Langerhans Cells

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7
Q

What are the main effector cells in the adaptive immune system of the eye?

A

CD4+ T cells
CD8+ T cells
B cells

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8
Q

Where are the Langerhans cells found in the eye and what is their function?

A

Abundant at corneo-scleral limbus, some in peripheral corneal (non in central 1/3rd)

Principle APC - rich in MHC Class II

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9
Q

Which part of the eye has lymphatic drainage?

A

Conjunctiva

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10
Q

What cells are found in the mucosa associated lymphoid tissue (MALT) at the conjunctiva?

A

Macrophages
Langerhan’s cells
Mast cells

If recruited may also find neutrophils and eosinophils

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11
Q

Which type of APC are present at conjunctiva?

A

Dendritic

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12
Q

What immune cells are present in the sclera and cornea?

A

Very few - Lagerhan’s in peripheral but no lymphatics or lymphoid tissue.

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13
Q

What lymphoid populations are found in Lacrimal Gland?

A

More plasma cells (IgA) and CD8+ T cells than conjunctiva

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14
Q

What areas of the body have immune privilege?

A

Brain/CNS
Testes
Placenta/Foetus
Eyes - cornea, anterior chamber, lens, vitreous cavity, subretinal space

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15
Q

What components of the eye allow for immune privilege to occur?

A

Blood tissue barrier
Lack of lymphatic drainage
Rich in immunosuppressive molecules
Anterior chamber associated immune deviation (ACAID)

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16
Q

What is ACAID?

A

Anterior chamber associated immune deviation - peripheral tolerance to ocular antigens

Protects the eye from collateral damage of an immune response to infection by suppressing future responses

17
Q

What are the immunological hallmarks of ACAID?

A
  1. Generation of primed CD4+ T and B cells that produce non-complement-fixing antibodies
  2. Inhibition of delayed type hypersensitivity and B cells that produce complement fixing antibodies
18
Q

What is Sympathetic Ophthalmia?

A

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

19
Q

What cell type are the primary mediators in Sympathetic Ophthalmia?

A

T cells:
Initial wave - CD4+ helper
Later wave - CD8+ cytotoxic

20
Q

What are Gel and Coomb’s Classifications of Hypersensitivity?

A

Type I - Immediate, IgE mediated
Type II - Cytotoxic, direct cell killing
Type III - Immune complex mediated
Type IV - Delayed cell mediated

21
Q

Describe how sensitisation to an antigen occurs.

A
  1. APC presents Antigen to naive T cell
  2. T cell + Antigen + IL-4,5,9,13 –> differentiation to Th2
  3. Signals to B cells to class switch from IgM to IgE production
  4. IgE amplifies T cell response, mast cells bind remaining IgE
22
Q

Describe what occurs when mast cells re-encounter an antigen, resulting in hypersensitivity.

A

Allergen + Mast cell –> degranulation

Release of vasoacitive mediators (histamine and tryptase)
Increased production of cytokines and leukotrienes

23
Q

Give an example of a Type 1 Hypersensitivity in the eye.

A

Acute Allergic Conjunctivitis

24
Q

What is Chemosis?

A

Oedema of the conjunctiva

Non-specific sign of eye irritation

25
Q

What cell types are mainly involved in Type II Hypersensitivity?

A

Macrophages
Natural Killer Cells

Complement (membrane attack complex)

26
Q

Give an example of Type II Hypersensitivity.

A

Ocular Cicatricial Pemphigoid (autoimmune conjunctivitis)

27
Q

Give an example of Type III Hypersensitivity

A

Autoimmune Corneal Melting (may lead to perforation)

28
Q

Describe the sensitisation of intracellular pathogens in type IV hypersensitivity.

A

1 . APC - macrophages present to T cells

  1. Cells differentiate to TH1 cells
  2. Clonal expansion (some T and B memory)
29
Q

Describe how Type IV hypersensitivity occurs following sensitisation.

A
  1. Re-exposure attracts macrophages
  2. Exaggeration immune response - TH1 products (IFN-y, TNF-B, IL-2, IL-3, IL-8, MCAF, MIF) and macrophage activation (MHCII, TNF, oxygen radical and NO)
30
Q

Give an example of Type IV Hypersensitivity

A

Corneal Graft Rejection (vascularisation of host cornea reaching donor tissue)

31
Q

Important cell types in Type I Hypersensitivity

A

APC - Dendritic (MHCII)
TH2
B cells (IgE)
Mast cells

32
Q

Important cell types in Type II Hypersensitivity

A

Antibody - IgG
NK Cells
Complement –> Macrophages

33
Q

Important cell types in Type III Hypersensitivity

A

Antibody - IgG

Complement –> Neutrophil

34
Q

Important cell types in Type IV Hypersensitivity

A

APC: Macrophages
TH1
Macrophages (accumulation)

Y2 Opthalmology (5 decks)

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