Lecture 18 - Tolerance and Immune regulation Flashcards
How is self-reactivity restrained within a healthy immune system?
- Limiting production of self-reactive T and B cell clones
- Preventing unwanted destructive response by any clones
What is self-tolerance?
A failure to respond to intrinsic self-antigens
True or False? Self tolerance is inherited.
False
It is acquired
What is clonal deletion?
When an immature lymphocyte binds an antigen to its receptor
It dies!
What are the mechanisms that contribute to tolerance?
- Inactivation of self-reactive clones
- Immune regulation
- Self-epitopes not available for recognition
How is tolerance established?
- First by central tolerance
- Secondly by peripheral tolerance
How is central tolerance in B-cells acquired?
At the immature B-cell stage it is tested to see if the receptors will bind to self antigens
How can soluble or low-affinity self molecule be saved?
- Via receptor editing
- The receptors can be changed for a non-self binder
What are the stages of developement for a T-cell? [3]
> Double negative thymocytes
Double posative thymocytes (CD4 + CD8)
Single posative thyomyocytes (CD4 or CD8)
What checkpoint ensure that harmful T-cells aren’t made?
- T-cells that fail to make functional receptors
- Receptors that can’t recognise self-MHC
- Receptors that recognise self-MHC too strongly
What is peripheral tolerance?
When self-reactive T and B cells enter the periphery
What is the main cause for peripheral tolerance in B-cells?
A lack of T-cell help
What is the effect Treg has on T-cells?
It can inhibit harmful T-cells
What is Immunological privilege?
Antigens in these places do not elicit destructive immune responses
What can cause a tissue to become immunologically privileged?
- Enclosed by a physical barrier (selective entry)
- Low MHC I
- Rich in suppressive cytokines, eg TGFβ
- Express FasL
