Immunology Flashcards
(34 cards)
What aspects of eye physiology contribute to the barrier aspect of the innate immune system?
Blink reflex
Physical and chemical properties of eye surface
Limited exposure/size
How do tears physically aid the innate immune system?
Flushing of the eye
Mucous layer anti-adhesive
How do tears chemically aid the innate immune system?
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)
What immune cells in the eye are part of the innate immune system?
Neutrophils
Macrophages
Conjunctival Mast Cells
What are the 3 main requirement of the adaptive immune system?
- Antigen presenting cells
- Lymphatic drainage
- Effector cells
What are the APCs in the adaptive immune system of the eye?
Dendritic cells
B cells
Macrophages
Langerhans Cells
What are the main effector cells in the adaptive immune system of the eye?
CD4+ T cells
CD8+ T cells
B cells
Where are the Langerhans cells found in the eye and what is their function?
Abundant at corneo-scleral limbus, some in peripheral corneal (non in central 1/3rd)
Principle APC - rich in MHC Class II
Which part of the eye has lymphatic drainage?
Conjunctiva
What cells are found in the mucosa associated lymphoid tissue (MALT) at the conjunctiva?
Macrophages
Langerhan’s cells
Mast cells
If recruited may also find neutrophils and eosinophils
Which type of APC are present at conjunctiva?
Dendritic
What immune cells are present in the sclera and cornea?
Very few - Lagerhan’s in peripheral but no lymphatics or lymphoid tissue.
What lymphoid populations are found in Lacrimal Gland?
More plasma cells (IgA) and CD8+ T cells than conjunctiva
What areas of the body have immune privilege?
Brain/CNS
Testes
Placenta/Foetus
Eyes - cornea, anterior chamber, lens, vitreous cavity, subretinal space
What components of the eye allow for immune privilege to occur?
Blood tissue barrier
Lack of lymphatic drainage
Rich in immunosuppressive molecules
Anterior chamber associated immune deviation (ACAID)
What is ACAID?
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
What are the immunological hallmarks of ACAID?
- Generation of primed CD4+ T and B cells that produce non-complement-fixing antibodies
- Inhibition of delayed type hypersensitivity and B cells that produce complement fixing antibodies
What is Sympathetic Ophthalmia?
Rare, bilateral granulomatous uveitis (due to trauma or surgery to one eye)
What cell type are the primary mediators in Sympathetic Ophthalmia?
T cells:
Initial wave - CD4+ helper
Later wave - CD8+ cytotoxic
What are Gel and Coomb’s Classifications of Hypersensitivity?
Type I - Immediate, IgE mediated
Type II - Cytotoxic, direct cell killing
Type III - Immune complex mediated
Type IV - Delayed cell mediated
Describe how sensitisation to an antigen occurs.
- APC presents Antigen to naive T cell
- T cell + Antigen + IL-4,5,9,13 –> differentiation to Th2
- Signals to B cells to class switch from IgM to IgE production
- IgE amplifies T cell response, mast cells bind remaining IgE
Describe what occurs when mast cells re-encounter an antigen, resulting in hypersensitivity.
Allergen + Mast cell –> degranulation
Release of vasoacitive mediators (histamine and tryptase)
Increased production of cytokines and leukotrienes
Give an example of a Type 1 Hypersensitivity in the eye.
Acute Allergic Conjunctivitis
What is Chemosis?
Oedema of the conjunctiva
Non-specific sign of eye irritation
