Week 6 Flashcards
What is an autoimmune response?
A response directed against self-antigens that causes tissue damage or altered physiological function resulting from the autoimmune response.
What is attacked in terms of an autoimmune disease?
Usually the host proteins but can be nucleic acids.
What is self tolerance?
The bodies protective mechanism that prevents the development of autoimmune diseases.
In self tolerance, describe gene rearrangement.
Random
What does the random rearrangement of genes in self tolerance lead to?
Generation of lymphocytes that are specific for self-antigens.
What happens to self-reactive T and B cells during self tolerance?
They are destroyed or down-regulated.
Where does central tolerance occur?
Thymus (T cells) or Bone Marrow (B cells)
What is the mechanism of central self tolerance?
Clonal deletion
What is the site of peripheral self tolerance?
Everywhere in the body.
What is the mechanism for peripheral self tolerance?
Anergy, cell death or immune deviation.
Where do T cells originate and develop?
Originate in the bone marrow but develop in the Thymus.
In central self tolerance, what is the first step?
Antigen presenting cells present self-peptides to T cells and the cells can then undergo selection or apoptosis.
In central self tolerance, which cells survive positive selection?
Only the cells whose receptors interactions with self-MHC and self-peptide low affinity survive.
In central self tolerance, what happens in negative selection?
Cells that bind with high affinity to the self-MHC and peptide are deleted.
In central self tolerance, what cells undergo apoptosis?
Cells that fail to interact with self MHC and peptide.
What may happen to some self-reactive T cells that encounter self antigens during central self tolerance?
Some self-reactive T cells that encounter self-antigens in the Thymus develop into T regulatory cells followed by B cell initiated changes in receptors in the bone marrow.
Why is T cell tolerance often regarded as more important than B cell tolerance?
CD4 T cells have a central role in controlling nearly all immune responses. Whereas most B cells will not be able to produce autoantibodies unless the receive appropriate T cell help.
What happens to B cells in the bone marrow, whose receptors are cross-linked by self-antigens?
They are deleted or become self-tolerant.
What happens to T cell’s that do not have any T cell receptors expressed during self tolerance?
Cellular death
What happens to T cells which have T cell receptors with no recognition of self MHC during self tolerance?
Death by default
What happens to T cells which have T cell receptors with strong recognition of self MHC in self tolerance?
Negative selection (signalled death).
What happens to T cells which have T cell receptors with weak recognition of self MHC in self tolerance.
Positive selection
What happens to T cells if they are positively selected for during self tolerance?
Survival and maturation
What are the processes that can occur to peripheral auto reactive cells in peripheral self tolerance?
Clonal detection
Clonal anergy
Regulation and supression