L15 T cells Flashcards
what happens at sites of infection and inflammation in tissue
Dendritic cells take up antigen and present it on MHC
where do DC go after being at a site of infection
move to the lymph node
where do the naïve T cells come from (before entering and circulating the lymph node)
high endothelial venules (HEV)
what happens between the naïve T cells and Dc in the lymph node
the T cells scan the DC for peptides present on MHC
what must a T cell have in order to be activated by a DC
the right receptor to recognise the peptide present on MHC
names of activated T cells
CD4 helper cells
CD8 helper cells
what do the cytokines produced by T cells do?
make macrophages more bactericidal
example of a cytokine T cells can produce
IFN- gamma
what do CD4 helper cells do
activate B cells
produce cytokines
What do CD8 T cells do after being exposed to cytokines released by CD4
become cytotoxic by producing perforin and granzyme (cell-killing enzymes)
what part of both T and B cell antigen receptors interact with the peptides expressed on MHC
variable regions
why is it important for antigen receptors to have variable regions
so that they bind a range of peptides
what is a CAR T cell
chimeric antigen receptor
-an artificial receptor that recognises cancer cell antigens and triggers the T cell to produce cancer antigens
what do naive T cells form from
stem cells
what do the naive T cells (stem cells) do before entering the thymus
circulate the blood
where are T cells educated
thymus
what happens to T cells once in the thymus
stimulated to undergo rearrangement of the genes that code for the T cell receptors (mean receptors can be expressed)
what is clonal expansion
when a T cell comes into contact with an antigen
-T cell divides like crazy
what happens to the other T cell with different antigen receptors
no clonal expansion
-just stays silent
what kind of cells in the thymus kill off unwanted T cells
nurse cells (specialised dc)
what are developing thymocytes
very immature T cells
what happens to the thymocytes while in the thymus
passed over thymic stroma which expresses self-peptide on MHC I and II
Ability to bind to self MHC is tested
why is the thymus so useful when testing immature T cells
it produces a wide range of antigens found throughout the body
what happens to T cells that don’t elicit a response to MHC with self-peptide
it is considered a useless T cell
death by neglect
left to die,
what happens if the T cell has a moderate signal from the MHC self-peptide
positive selection
T cell continues out of the thymus
what happens when the T cell elicits a strong response with the MHC self-peptide
cell is programed to die
how do auto immune disorders come about
whne the self peptide is expressed at too low a level in the thymus and so the T cells that strong interact with it make it through the thymus and then interact elsewhere in the body
what are the positive selected T cells called
self MHC restricted
What problems can occur due to the different MHC between different people
Specific T cells for a virus can only interact with the MHC that expressed the virus when if the peptide is the same
what is teh cause of transplant rejection
subset of mature T cells that recognise foreign MHC on the organ (5% of T cells)
what percent of T cells are alloreactive
1-5%
what happens during an allogenic reaction
T cells expand
what happens during an allogenic reaction
T cells react strongly to foreign MHC that is loaded with self peptide from the donor organ
how are transplant rejections prevented
matching MHC
or powerful immuno suprresant to knock back the T cells
transplant reactions occur due to
polymorphic MHC
what does xenogeneic mean
different species
what does autologous mean
self to self
what does syngeneic mean
identical twins
what does allogeneic reaction mean
self to non-identical of same species
