AED - Immunopathology - Week 1 Flashcards
Are lymphatic vessels present intraocularly? What about in the eye and orbit? What is this a major factor of?
None are present intraocularly, and generally scarce in the eye and orbit
Major factor in the eyes immune privilege
List where in the eye lymphatic vessels can be found (7).
Conjunctiva
Limbus
Lacrimal gland
Eyelid
Optic nerve dura sheath
EOMs
Choroid (controversial)
What are MALTs?
Mucosa-associated lymphoid tissue where B and T cells can migrate to
What kind of cells are mainly found in lacrimal gland MALTs? What other cells are they associated with?
IgA-positive plasma cells
Associated with grouped and individually patrolling T cells
What two cells are predominantly found in MALTs found in canaliculae and lacrimal mucosa?
T cells and macrophages
Define intraocular immune privilege.
Sites in the body where foreign tissue grafts can survive for extended or indefinite periods of time, whereas similar grafts placed at conventional body sites are acutely rejected.
Are there excessive immune responses within the blood-ocular barrier?
No
Give three pieces of evidence for intraocular immune privilege.
Foreign tissue placed in the anterior chamber is not rejected
Unrestricted growth of allogenic (non-self) tumour cells inside the eye
Aqueous and vitreous fluids inhibit inflammatory cells in vitro
Expression of what compound and by which cells contributes to intraocular immune privilege?
TGF-B2 by pigmented cells in the eye
High levels of TGF-B2 are found in eye, not so in other tissue
How does TGF-B2 inhibit immune response in the eye?
Disarms T-cells that cross the pigmented epiithelium
What is the role of a-MSH in the eye (2)?
Inhibits macrophage activation and promotes production of anti-inflammatory factors
List three mechanisms of intraocular immune privileges and explain how if applicable.
Physical barrier
-efficient BRB, no efferent lymphatics
Inhibitory microenvironment
Active regulation of the immune response
-anterior chamber acquired immune deviation
Define the following:
Autoimmunity
Hypersensitivity
Immune deficiency
Autoimmunity - failure to distinguish self from non-self
Hypelsensitivity - excess/inappropriate response
Immune deficiency - absent/inadequate response
What results almost exclusively from a viral or chlamydial infection and sensitivity to topical medication and in what two regions of the eye? Where are the vessels, and is there a damaging collateral response?
Follicles: raised gelatinous lesions of the upper and lower tarsal and bulbar conjunctiva
Surrounding (not central) blood vessels
No damaging collateral response
What are conjunctival follicles histologically and are they present on a normal conjunctiva?
When these regions are selectively stained for B-lymphocytes, what is revealed and what does it resemble?
Flat, defined accumulations of lymphocytes and are present in normal conjunctiva
With selective staining, it indicates a germinal centre, much like lymph nodes