Immunology Flashcards
What is the purpose of the immune system?
To identify and eliminate harmful stimuli
What are the two types of immunity?
Innate
Adaptive
Briefly describe the innate immune response
Fast acting
No memory
Broad response to limited number of stimuli
Briefly describe the adaptive immune response
Slower to act
Memory of pathogen
Specific to pathogen
What are some of the physical protections the eye possess?
Little physical barrier but does have eyelid and conjunctiva.
Few commensal bacteria
Chemical agents such as lipids
Tears
What is the purpose of tears?
Flush the eye
Provide an anti-adhesive surface to prevent colonisation
Contains antibacterial chemicals and cells
What are the three layers of tears?
Lipid layer
Aqueous layer
Mucin layer
What immune cells can be found in tears?
Neutrophils
Macrophages
Conjunctival mast cells
How do neutrophils work?
Chemotaxis and secrete enzymes etc to damage bacteria
How do macrophages work?
Phagocytose cells and stimulate rest on immune system
What factors are required for the adaptive immune response?
Antigen presenting cells- dendritic, B cells, macrophage
Lymphatic drainage
Effector cells- CD4+, T cells, CD8+, B cells
What specific antigen presenting cells can be found in the external layers of the eye?
Langerhans cells
Less in number as move inside from sclera to cornea
Which is the only part of the eye with lymphatic drainage?
Conjunctiva
Where does the conjunctival lymphatic drainage go?
Mucosa associated lymphoid tissue
What is mucosa associated lymphoid tissue?
Not an lymph node but similar- Cluster of immune tissue
What is the primary defense of the eye from infection?
Tough sclera and cornea
Describe some of the disadvantages of the eye for fighting infection?
Avascular
Few APC
No lymph tissue
Down Regulated immune environment
What is another term for a down regulated immune environment?
Immune privilege
What is immune privilege?
Ability to tolerate introduction of antigen without eliciting immune response therefore protecting tissue
What is sympathetic ophthalmia?
When damage to one eye can cause blindness in the other
What causes sympathetic ophthalmia?
Damage to one eye causes release of eye specific antigens.
Antigens activate T cells in lymph nodes.
As T cells cannot tell difference between eyes they act on both causing damage to previously fine eye.
What is a hypersensitivity reaction?
Where an immune response causes damage to the tissues too.
How many types of hypersensitivity reaction are there?
4
What are the 4 types of hypersensitivity reaction?
1- Allergic/acute
2- Antibody mediated
3- Complex (immune complex)
4- Delayed
Briefly describe the mechanism behind type 1 hypersensitivity
B cells produce antigen specific IgE antibodies which deal with antigen.
Remaining IgE binds to Mast cells.
When antigen next encountered IgE triggers mast cells to release histamine and cause issues
What cells and antibodies are involved in type 1 hypersensitivity
B cells
Mast cells
IgE
What is an example of type 1 hypersensitivity in the eye?
Acute allergic conjunctivitis
What happens in type 2 hypersensitivity?
Immune cells directly attack self tissue
What cells are involved in type 2 hypersensitivity?
Macrophages
NK cells
Membrane attack complex
Give an example of type 2 hypersensitivity in the eye
Ocular cicatricial pemphigoid
How does type 3 hypersensitivity cause problems?
Antibodies and antigen form large complexes which can block vessels and direct immune attack to self tissue
Give an example of type 3 hypersensitivity in the eye
Autoimmune corneal melting
Describe type 4 hypersensitivity
Previous exposure primes Helper T cells
When re-exposed you get an exaggerated immune response
Give an example of type 4 hypersensitivity in eyes
Corneal graft rejection
