The development of T lymphocytes Flashcards
where do T cells develop (start off with an easy one ;) )
thymus
as we age does the thymus degrade
yes
do thymocytes commit to the T cell lineage before rearranging their T cell receptor genes
yes
how long does it take with interaction of thymic stomal cells for them to become thymocytes
1 week
what do double negative cells mean
we dont know if they will be helpful or cytotoxic T cells (CD8 and CD4)
does the RAG complex become activated when the uncommitted progenitor cell turns into a double negative thymocyte committed to the T cell lineage
yes
does the CD34 stay positive when the uncommitted progenitor cell turns into a double negative thymocyte committed to the T cell lineage
no it becomes negative
does Notch signaling drive T cell development
yes
notch signaling pathway
notch ligand binds to notch 1, bond between gets cut in the thymocyte, then travels into the nucleus in order to activate transcription of T cell development
which genes start at the beginning of T cell lineages
gamma, delta and beta genes start racing
what happens if the beta chain recombines first
you have an uncommitted double negative thymocyte
what happens with the uncommitted double negative thymocyte from the beta chain recombining
another race happens where alpha takes over betas place
what happens if alpha gene wins the race
the cell becomes and committed alpha-beta T cell which is functional and expresses CD8 and CD4 receptors
what happens if gamma and delta rearrange the cell first
the T cell will move on as a gamma-delta T cell receptor
what percentage of thymocytes are successful and then which cells clean up after them
2%, macrophages
what does VDJ rearrangement result in
beta and delta genes
what does VJ rearrangement result in
alpha and gamma genes
what is the developmental pathway determined by
which can make productive rearrangements, get to the cell surface and start signalling
why does the beta chain normally win?
rearranging 1 chain is easier than rearranging 2 (gamma and delta)
when does rearrangement of the alpha chain occur
in pre-T cells
do all the beta chains look the same because of allelic exclusion?
yes
do the alpha chains all look different and why
they all look different which allows for diversity in the cells
what does CD4 and CD8 expression induce
double positive thymocytes
how many checkpoints are there during early T cell development
2
what happens when T cells recognize self-MHC molecules in the thymus
theyre positively selected
when there is moderate or strong binding the positive thymocyte binds to MHC molecules and lives: T or F
true
what happens when there is weak binding between the negative thymocyte and the MHC molecules
they die
what does positive selection determine
the expression of either the CD4 or the CD8 co-receptor
what happens when T cells recognize self antigens in the thymus
they are removed by negative selection
what is the function of negative selection of thymocytes in the thymus
to eliminate autoreactive thymocytes
when there is tight binding between a negative thymocyte to the MHC molecules what happens
the cell dies
when there is moderate binding between a positive thymocyte to the MHC molecules what happens
cell lives
