Immunology

Question 1

What is involved in the immediate-innate immune response?

Answer 1

Anti-microbial properties, complement, mast cells, macrophages, inflammation

Question 2

What is involved in the early-innate immune response?

Answer 2

Recruitment/activation of phagocytes, inflammation

Question 3

What are some components of the innate immune system involved in defence?

Answer 3

Physical barrier, commensal bacteria, chemical agents, cells

Question 4

What are some solutions to the eye being exposed and not protected?

Answer 4

Blink reflex, physical and chemical properties of eye surface, limit exposure/size

Question 5

What are the physical properties of tears?

Answer 5

Flushing, mucous layer-antiadhesive

Question 6

What are the chemical properties of tears?

Answer 6

Lysozyme (gram -ve, fungi), lacto/transferrin (gram +ve), complement, Tear lipids (antibacterial to cell membranes), secretory IgA (prevents attachment)

Question 7

What are the cellular properties of tears?

Answer 7

Neutrophils- attracted by chemotaxis, scavengers:release free radicals, enzymes. Macrophages- phagocytosis of damaged cells, helps to trigger adaptive/ Conjunctival mast cells-vasoactive mediators

Question 8

What does the acquired immune system require?

Answer 8

Antigen presenting cells, lymphatic drainage to node

Question 9

What are the immune properties of the conjunctiva?

Answer 9

Only part of eye with lymphatic drainage, dendritic cells- act as APCs, MALT, commensal bacteria

Question 10

What are the immune properties of the cornea and sclera?

Answer 10

Tough collagen coat, avascularity, downregulated immune environment, lack of APCs

Question 11

What are the immune properties of the vitreous, choroid and retina?

Answer 11

Blood-ocular barrier, relative lack of APCs, downregulated immune environment

Question 12

What is immune privilege?

Answer 12

Sites are able to tolerate the introduction of antigens without eliciting an inflammatory immune response

Question 13

What sites have immune privilege?

Answer 13

Brain/CNS, testes, placenta/foetus, eyes

Question 14

What ocular immune privileges mechanisms exist?

Answer 14

Unique anatomical feature of blood barrier and a lack of direct lymph drainage, ocular microenvironment is rich with immunosuppressive molecules that influence the activity of immune cells, placement of foreign antigen into the ocular microenviornment can induce a systemic form of tolerance to the foreign antigen called anterior chamber-associated immune deviation (ACAID_

Question 15

What is sympathetic ophthalmia?

Answer 15

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

Question 16

How is sympathetic ophthalmia caused?

Answer 16

Thought to be 2’ to development of AI reaction to ocular antigens that are exposed during traumatic or surgical event

Question 17

What are the primary mediators of sympathetic ophthalmia?

Answer 17

T cells- Initial wave CD4+ and later is CD8+ cytotoxic

Question 18

What are the injured and non-injured eyes known as in sympathetic ophthalmia?

Answer 18

Exciting and sympathising eye

Question 19

How do both eyes appear clinically in sympathetic ophthalmia?

Answer 19

Appear the same-only by history can exciting eye be identified

Question 20

What is the immune response in sympathetic ophthalmia?

Answer 20

Trauma to one eye results in release of sequestered intraocular protein antigens. Released intraocular antigen is carried to LNs and activates T cells. Effector T cells return via bloodstream and encounter antigen in both eyes

Question 21

What is the classification of hypersensitivity reactions?

Answer 21

Type I: Immediate hypersensitivity
Type II: Direct cell killing
Type III: Immune complex mediated
Type IV: Delayed type hypersensitivity

Question 22

What is the role of mast cells in allergic reaction?

Answer 22

Express receptors for Fc region of IgE antibody on their surface

Question 23

What happens in an immediate hypersensitivity reaction?

Answer 23

Allergen encounter> B cells produce specific IgE Ab, Allergen is cleared. Residual IgE Ab bind to circulating mast cells via Fc. Re-encounter with allergen, allergen binds to IgE-coated mast cells and disrupts cell membrane. Release of vasoactive mediators (histamine, tryptase, also increased cytokines and LK transcription)

Question 24

What is chemosis?

Answer 24

Oedema of conjunctiva

Question 25

When can chemosis occur?

Answer 25

Acute allergic conjunctivitis

Question 26

In a Type II reaction, what are cells killed by?

Answer 26

Macrophages/NK cells, complement (MAC)

Question 27

What is ocular cicatrical pemphigoid an example of?

Answer 27

Type II hypersensitivity

Question 28

What is the pathway in a type III immune complex mediated reaction?

Answer 28

Little Ab, excess antigen. Small complexes form that do not fix complement, and not cleared from circulation. At intermediate stages, comparable amounts present. Large complexes form that fix complement and are cleared. Late in response-large Ab and little antigen amounts. Medium-sized complexes form, fix complement and are cleared

Question 29

What type of reaction is AI corneal melting an example of?

Answer 29

Type III

Question 30

What is the pathway in a type IV delayed type hypersensitivity reaction?

Answer 30

T helper cells activated in sensitisation phase, they recognise macrophages (MHC2) and clonal expansion occurs. CD4+ secrete IL2 and IFgamma, further inducing release of Th1 Cytokines. In effector phase when macrophages are re-exposed, activation occurs

Question 31

What type of reaction is corneal graft rejection an example of?

Answer 31

Type IV hypersensitivity