10.7 Autoimmunity and Hypersensitivity Flashcards
What is a hypersensitivity reaction?
Inappropriate and/or exaggerated response to an antigen, leading to an over-reacting inflammatory response and destruction of innocent cells
What is Type 1 hypersensitivity also called?
Allergic reaction
Which Ig isotype mediates type I hypersensitivity reactions?
IgE
What can predispose someone toward generating high levels of IgE antibodies?
Atopy (atopic patients)
Which type of molecule triggers a type 1 hypersensitivity reaction?
Allergen
Draw a map of the action of (and predisposition to) IgE, and its influence on type 1 hypersensitivity responses
(Cytokines: IL-4 and IL-5)
See document
What type of hypersensitivity response is asthma?
Type 1 (allergic response)
Describe the late phase of a type 1 hypersensitivity reaction
- Occurs after initial degranulation of mast cells with IgE
- Esoinophins play a major role in inflammation
- This can result in permanent tissue damage and remodelling
How long does type 1/type 4 hypersensitivity take to occur?
Type 1: Within an hour max
Type 4: Days (>72 hours)
Why does type 4 hypersensitivity take longer than type 1 hypersensitivity?
Requires recruitment and proliferation of cells as opposed to simple degranulation or enzymatic reactions
Which isotype of antigens are involved in type 4 hypersensitivity?
None of them. Only cells
What type of antigens can trigger type 4 hypersensitivity?
- Hapten
- Contact antigens
- Intracellular pathogens
Draw a mech of type 4 hypersensitivity
Document
Do antigens need to be presented on MHC in order to be recognised by B cells?
No: B cell receptors are surface immunoglobulins
Briefly describe screening of B and T cells
B Cells: Tested to see if they bind to self antigen (yes: apoptosed, no: lives and exits bone marrow)
T Cells: Same; if lives, exits thymus
These must occur separately to minimise chances of autoimmunity
