wk1: AED - Immunopath Flashcards
Are lymphatic vessels present intraocularly?
No. However, they are present on the edge of the limbus and on the conjunctiva, among some other places
Where in the eye and orbit does the lymphatic system exist?
Conjunctiva
Limbus
Lacrimal Gland
Optic Nerve (dural sheath)
Eyelid
EOMs (connective tissue)
Choroid?? (controversy!)
What does MALT stand for?
Mucosa Associated Lymphoid Tissue
What is the function of MALT?
MALT inductive sites are secondary immune tissues where antigen sampling occurs and immune responses are initiated
Describe the cellular makeup of MALTs in the lacrimal gland
Mainly IgA-positive plasma cells, associated with grouped and individually patrolling T cells
Describe the cellular makeup of MALTs found in canaliculae and lacrimal mucosa
Predominantly T cells; Macrophages plentiful
Name 3 locations where MALTs can be found
Lacrimal Gland
Canaliculae
Lacrimal Mucosa
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 in other regions get rejected)
Name an example of a location where intraocular immune privilege takes place
Cornea
From an immune standpoint, what differs between the eye and other tissues of the body that provides intraocular immune privilege
TGF-B2 levels are high in the eye (whereas not high in other tissues)
Where in the eye is TGF-B2 expressed?
expressed by pigmented cells of the eye (RPE, PE of ciliary body and iris)
Name 8 cells or proteins involved in innate immunity
complement proteins, granulocytes (basophils, eosinophils, neutrophils), mast cells, macrophages, dendritic cells, natural killer cells
What is the role of TGF-B2 expression in the eye?
inhibit immune response
What is the role of a-MSH expression in the eye? [2]
Inhibits macrophage activation and promotes production of anti-inflammatory factors
Name the 3 mechanisms behind intraocular immune privilege
Physical barrier
Inhibitory microenvironment
Active regulation of the immune response
How does a physical barrier provide intraocular immune privilege? [2]
Efficient BRB, no efferent lymphatics
How does the eye actively regulate the immune response to provide intraocular immune privilege?
ACAID (anterior chamber acquired immune deviation): eye derived antigens elicit a T-reg skewed response, in which DTH is suppressed
Expression of FAS ligand in cornea, iris and CB epithelium: actively induces infiltrating FAS+ T-cells to undergo apooptosis
Identify the pathogenic causes for the following clinical scenario: raised gelatinous lesions of upper and lower tarsal + bulbar conjunctiva, surrounding (not central) blood vessels, no damaging collateral response [3]
Viral or chlamydia infection or sensitivity to topical medication
What does the diffuse layer of conjunctival MALT contain?
plasma cells, lymphocytes (mix of CD4/CD8+ T-cells & unactivated B cells)
What are High endothelial venules (hev)?
specialised vessels that promote leukocyte extravasation. They enable circulating leukocytes to directly enter a lymph node (by crossing through the hev).
Where can you find high endothelial venules?
Present in all kinds of lymphoid tissue (e.g. lymphoid tissue/MALT in conjunctiva)
What are conjunctival follicles composed of?
Flat, defined accumulations of lymphocytes
Are follicular and diffuse lymphocyte layers beneath or in front of the conjunctival epithelial surface?
Beneath
Describe the steps in the development of follicular hyperplasia in the conjunctiva
- Antigen exposure to follicular and diffuse lymphocyte layers underneath the conjunctival epithelial surface
- Proliferation of appropriate lymphocyte population to produce memory cells and plasma cells
- Plasma cells migrate to the diffuse layer and release antibody + memory cells proliferate – causing follicular hyperplasia
– note: this is when you’ll see a raised bump on conjunctiva b/c epithelial tissue now displaced
Define hyperplasia
The enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells
What is Follicular Hyperplasia?
a type of lymphoid hyperplasia. Is caused by a stimulation of the B cell compartment. Is caused by an abnormal proliferation of secondary follicles and occurs principally in the cortex without broaching the lymph node capsule
What are the clinical signs that graft rejection has occurred in the eye? [5]
Red eye
Cells + plasma protein in ant. chamber
Corneal cellular infiltration + oedema
Corneal vascularisation
Keratic precipitates
Describe the histopathology of corneal graft rejection [3]
Infiltration of donor corneal button with many CD4+ & CD8+ T-cells
Cells from cornea move in from host limbal vessels
Later donor vascularisation
What 2 processes increase the likelihood of corneal rejection and how?
Corneal neovascularisation and lymphangiogenesis increases likelihood of graft rejection via reflex arc to lymph nodes
How might Rheumatoid Arthritis clinically manifest in the eye? [4]
Uveitis
Episcleritis
Scleritis
Red eye
Describe the histopathology of ocular changes with Rheumatoid Arthritis [3]
Characteristic lymphocyte and plasma cell infiltration of the iris in autoimmune anterior uveitis
Cells present in ant. chamber + adherent to corneal epithelium
Presence of Russell Bodies
What are Russell bodies?
eosinophilic, large, homogenous, immunoglobulin containing inclusions usually found in plasma cells undergoing extensive synthesis of immunoglobulin
In the ocular histopathology of rheumatoid arthritis patients, what forms around the necrotic collagen?
granulamatous cells
What are the clinical hallmarks of CMV retinitis? [2ish]
Mild granulomatous inflammation in the retina + choroid with retinal necrosis and choroidal granuloma
What changes to the retinal cells in CMV retinitis?
Retinal cells show multiple inclusion bodies in cytoplasm, which presumably contain the virus in them
What parts of the eye can Karposi’s Sarcoma involve? [3]
Eyelid, Conjunctiva, Orbit
