Immunology - Tolerance Flashcards
(75 cards)
After stem cells “choose” to become lymphoid progenitors, those progenitors divide under the influence of
IL-7
Unlike B-cells, T-cells undergo very little maturation in the bone marrow. They Need to travel to the ? to develop functional T-cell receptors
thymus
the thymus is located where?
superior to the heart, anterior to the great vessels
the thymus is largest when?
largest prior to puberty, shrinks afterwards
the thymus is divided into ?
cortex and medulla
T-cells with TCRs that can bind to antigen presented via HLA WILL survive ->
positive selection
T-cells with TCRs that bind self-antigen with high affinity WON’T survive ->
negative selection
what is the structure of the TCR?
2 chains: 1 alpha and 1 beta - each with a variable region and a constant region
the T-cell receptor is never what? (think location)
never secreted - it always stays attached to the membrane
T-cell precursors from the bone marrow enter the thymus from vessels at where?
the junction of the cortex and medulla
initially, when the T-cell precursors enters the thymus, they don’t express CD8 or CD4, they are known as ?
double negative (DN)
DN cells commit to a T-cell lineage and is known as ?
DN3 cells
DN3 cells are mostly found where?
in the cortex of the thymus
what do DN3 cells do before turning DN4?
genetically shuffle their TCRs
DN cells first rearrange what part of the TCR?
beta chain of the TCR
if the rearrangement of the beta chain of the TCR is done correctly, then proliferation continues and they become what?
DN4 cells
if the rearrangement of the beta chain of the TCR is done incorrectly, then proliferation continues and they become what?
the cell dies
what happens when DN3 cells turn to DN4
the alpha chain of the TCR is shuffled
after both TCR chains have been recombined, the developing T-cell expresses what?
both CD4 and CD8
what is it called when the T cell precursors expresses both CD4 and CD8?
double positive (DP)
what does DP cells do after recombined TCR do?
sample thymic epithelial cells HLA (with self-antigens expressed)
if the DP cells have a very low affinity interactions with HLA what happens?
death of the DP T-cell
if the DP cells have a medium-low affinity interactions with HLA what happens?
survival of the DP T-cell
if the DP cells have a high affinity interactions with HLA what happens?
death of the DP T-cell
