Immunology Flashcards
What are the solutions to the fact that the eye has no physical barrier?
blink reflec
physical and chemical properties
limit exposure/size
What comprises the blink reflex?
tears - physical protection
What is the tear film made up of?
outer lipid layer
aqueous layer - nourishes the eye
mucin layer - sticks everything to the eye and traps pathogens so they cannot go into the eye
What are the chemicals in tears meant to do?
destroy bacteria
What immune cells does the eye contain?
neutrophils
macrophages
conjunctival mast cells
What is the priniciple antigen presenting cell of the external eye?
Langerhan cells - rich in class 2 MHC molecules
What is the adaptive immune system of the eye?
antigen presenting cells eg - dendritic cells, B cells and macrophages
lymphatic drainage to the lymph nodes to start an immune reaction
effector cells - CD4 T cells, CD8 T cells, B cells
Where are Langerhan cells usually found in the eye?
abundant at the limbus
less in the peripheral cornea
absent from central 1/3rd
What is special about the conjunctiva?
only area in the eye with lymphatic drainage - contains specialised endothelial venules for regulated migration of lymphoid cells
contains MALT
What is MALT?
mucosal associated lymphoid tissue - clusters of immune cells
Describe the cornea and scleras immune system?
down regulated immune environment
tough collagen coat
no lymphatics or blood supply
lack of APCs
Describe the immune situation of the lacrimal gland?
more plasma cells (IgA) and CD8 tcells than conjunctiva
T cells stay in small groups in the intralobular ducts
Describe the immune situation of the lacrimal drainage system?
MALT tissue containing diffuse lymphoid tissue and follicles
What is the immune situation of the vitreous, choroid and retina?
downregulated immune environment
lack of APCs
blood-ocular barrier limits the spread between eye and blood
What parts of the eye have a downregulated immune environment?
vitrious choroid retina cornea sclera
What is immune privilege?
the ability of the eye to tolerate invading pathogens without elicting an inflammatory response
What sites in the eye have immune privilege?
cornea anterior chamber lens vitrous cavity subretinal space
What is immune privilege brought about by?
anterior chamber associated immune deviation (ACAID)
What is ACAID?
a tolerance can form to the pathogen because the active mechanisms down regulate the normal response
What are the immunological hallmarks of ACAID?
generation of primed CD4 T cells and B cells that produce non complement fixing antibodies
inhibition of delayed-type hypersensitivity and B cells that secrete complement fixing antibodies
What are the other mechanisms of immune privilege?
ocular microenvironment is rich in immunosuppressive molecules and inhibitory cell surface molecules
there are special antimicrobial features of the blood brain barrier
lack of lymphocytic drainage
What is sympathetic ophthalmia?
a rare bilateral granulomatous uveitis where one eye is affected initially, then the other
- disadvantage to immune privilege
- can leave person completely blind
What causes sympathetic opthalmia?
an autoimmune reaction to ocular antigens
What is the pathophysiology behing sympathetic opthalmia?
trauma to one eye results in the release of squestered intraocular protein antigens which are carried to lymph nodes to activate T cells
effector T cells return via blood stream to BOTH eyes and so both eyes develop the inflammatory reponse
