T Cells and B Cells. Flashcards
Where do all T cells mature?
In the thymus (T stands for thymus).
What happens to T cells once they arrive in the thymus?
They divide very rapidly and undergo somatic rearrangement.
Will T cells all express the same TCR?
No, the amount of diversity between the different TCRs that a T cell can express is huge.
What are the only somatic cells where somatic gene rearrangement takes place?
B and T cells.
What must happen to B and T cells before they can function?
They must be educated.
What are naive T cells also known as?
As thymocytes.
What is the name of the first step of T cell education?
Positive selection.
What occurs during the positive selection of T cells?
T cells bind to a self MHC and learn to recognise it.
This means that the T cell can recognise the MHC complexes of the body.
During positive selection what happens to the T cells that do not bind to a self MHC?
They are killed.
What is the 2nd step of T cell education?
Negative selection.
What occurs during the negative selection of T cells?
The T cell tries to bind to a self antigen.
During negative selection, what happens to T cells that form strong bonds with self antigens?
They will be killed.
What bonds do we want naive T cells to form self antigens?
Very weak bonds that are not strong enough to form an immune response.
What happens if the negative selection step of T cell education fails?
We can get an autoreactive T cell.
How long does T cell education in the thymus take?
Around 4-5 days.
What will be expressed by T cells that survive T cell education in the thymus?
CD-4 or CD-8 molecules.
What CD molecule is expressed by all T cells?
CD-3.
What are the CD molecules that can be expressed by the 2 types of T cells as they leave the thymus?
CD-3+ and CD-4+.
CD-3+ and CD-8+.
What happens to T cells once they have acquired the CD molecules?
They can migrate to the secondary lymphoid tissues.
Do naive T cells leave the thymus?
Yes.
Naive T cells enter the secondary lymphoid tissues.
Where do B cells mature in birds?
In the bursa.
Where do B cells mature in mammals?
In the bone marrow and in the Peyers patches.
What are Peyers patches?
The mammalian equivalent of a bursa.
Where in the body are peyers patches found?
All over the body.
