AED - Immunopathology - Week 1

Question 1

Are lymphatic vessels present intraocularly? What about in the eye and orbit? What is this a major factor of?

Answer 1

None are present intraocularly, and generally scarce in the eye and orbit
Major factor in the eyes immune privilege

Question 2

List where in the eye lymphatic vessels can be found (7).

Answer 2

Conjunctiva
Limbus
Lacrimal gland
Eyelid
Optic nerve dura sheath
EOMs
Choroid (controversial)

Question 3

What are MALTs?

Answer 3

Mucosa-associated lymphoid tissue where B and T cells can migrate to

Question 4

What kind of cells are mainly found in lacrimal gland MALTs? What other cells are they associated with?

Answer 4

IgA-positive plasma cells

Associated with grouped and individually patrolling T cells

Question 5

What two cells are predominantly found in MALTs found in canaliculae and lacrimal mucosa?

Answer 5

T cells and macrophages

Question 6

Define intraocular immune privilege.

Answer 6

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.

Question 7

Are there excessive immune responses within the blood-ocular barrier?

Answer 7

No

Question 8

Give three pieces of evidence for intraocular immune privilege.

Answer 8

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

Question 9

Expression of what compound and by which cells contributes to intraocular immune privilege?

Answer 9

TGF-B2 by pigmented cells in the eye

High levels of TGF-B2 are found in eye, not so in other tissue

Question 10

How does TGF-B2 inhibit immune response in the eye?

Answer 10

Disarms T-cells that cross the pigmented epiithelium

Question 11

What is the role of a-MSH in the eye (2)?

Answer 11

Inhibits macrophage activation and promotes production of anti-inflammatory factors

Question 12

List three mechanisms of intraocular immune privileges and explain how if applicable.

Answer 12

Physical barrier
-efficient BRB, no efferent lymphatics
Inhibitory microenvironment
Active regulation of the immune response
-anterior chamber acquired immune deviation

Question 13

Define the following:
Autoimmunity
Hypersensitivity
Immune deficiency

Answer 13

Autoimmunity - failure to distinguish self from non-self
Hypelsensitivity - excess/inappropriate response
Immune deficiency - absent/inadequate response

Question 14

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?

Answer 14

Follicles: raised gelatinous lesions of the upper and lower tarsal and bulbar conjunctiva
Surrounding (not central) blood vessels
No damaging collateral response

Question 15

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?

Answer 15

Flat, defined accumulations of lymphocytes and are present in normal conjunctiva
With selective staining, it indicates a germinal centre, much like lymph nodes

Question 16

Are T-cells found in conjunctival follicles?

Answer 16

Yesd, much like lymph nodes

Question 17

What cells does the diffuse layer of the conjunctival MALT contain (5)?

Answer 17

Plasma cells
Lymphocytes
Mix of CD4+ and CD8+
Unactivated B-cells

Question 18

What vessels of note can be found in the diffuse later of the conjunctival MALT and what do they do?

Answer 18

High endothelial venules, which are specialised vessels that promote leukocyte extravasation

Question 19

Describe, in four steps, the model of pathogenesis of follicular hyperplasia in the conjunctiva.

Answer 19

Follicular and diffuse layers are beneath the conjunctival epithelium
Antigen exposure occurs
Proliferation of appropriate lymphocyte population to produce plasma and memory cells
Plasma cells migrate from the follicle to the diffuse layer, releasing antibodies, causing follicular hyperplasia, and memory cells proliferate

Question 20

List 6 clinical features of a rejected corneal graft.

Answer 20

Red eye
Cells and plasma proteins in the anterior chamber
Corneal cellular infiltration
Oedema
Corneal vascularisation
Keratic precipitates

Question 21

Describe the histopathology of a corneal graft rejection.

Answer 21

Infiltration of donor corneal button with many CD4+ and CD8+ T cells, which move in from host limbal vessels

Question 22

What do corneal neovascularisation and lymphangiogenesis increase the likelihood of and how?

Answer 22

Graft rejection via a reflex arc to lymph nodes

Question 23

Define rheumatoid arthritis and 4 ways it can manifest in the eye.

Answer 23

Cell mediated autoimmune condition

Uveitis, episcleritis, scleritis, dry eye

Question 24

Describe the histopathology of ocular changes associated with rheumatoid arthritis (4).

Answer 24

Lymphocytic and plasma cell infiltration of the iris
Cells also in the anterior chamber and andherent to the corneal endothelium
Presence of Russell bodies
Advanced scleritis
Evidence of granulomatous cell formation around necrotic collagen

Question 25

Define Russell bodies.

Answer 25

Inclusions in/ modifications of plasma cells which contain excessive immunoglobin

Question 26

Advanced scleritis in rheumatoid arthritis is driven by the activity of what two cells?

Answer 26

T-cell and macrophage activity.

Question 27

What is the most common ocular manifestation of AIDS?

Answer 27

Retinopathy

Question 28

What viruses are generally responsible for AIDS retinopathy (2)?

Answer 28

HIV or CMV

Question 29

List three hallmarks of CMV retinitis.

Answer 29

Mild granulomatous inflammation in the retina and choroid
Retinal necrosis
Choroid granuloma

Question 30

What do retinal cells show in CMV retinopathy?

Answer 30

Multiple inclusion bodies in their cytoplasm

Question 31

What percentage of individuals have CMV with AIDS retinopath?

Answer 31

85=90%

Question 32

Are the hallmarks of CMV retinoapthy commonly seen in non-immunocompromised individuals?

Answer 32

No, rarely seen

Question 33

What kind of tumour is commonly seen in AIDS patients? What three structures of the eye can it involve? What is it largely due to?

Answer 33

Kaposi’s sarcoma - a vascular tumour
Can involved the eyelid, conjunctiva, and orbit
Largely due to reduction in CD4+ T cells