Lymphocyte Development Flashcards
(44 cards)
Cells entering the thymus
are not yet committed to becoming a lymphocyte and express no antigen-specific receptors
Cell leaving the thymus are
mature-functional T cells and express antigen specific T cell receptors
TCRs are both
- self-tolerance (-)
2. Restricted to self- MHC (+)
Where do T cells develop
thymus (primary lymphoid organ)
Early T-cells precursor development occurs in
bone marrow
From the bone marrow the T-cell precursors
go to the thymus then to the medulla
T-cell double negative
cell has no CD4 or CD8 (CD4-CD8-)
T-cell double positive
Is both CD4+CD8+
T-cell positive/negative
stages for a cell to become single positive CD4+ or CD8+
Functional mature T-cells are released?
peripheral bloodstream
Recombination of the TCR gene segments occurs where?
Double negative stage
T cell development occurs in two stages
- Early thymocyte development
2. T cell maturation
NOTCH
commits cells to the T cell lineage
CD25
receptor for IL-2
Beta-selection
results in proliferation and after this occurred the thymocytes are at the DP stage of development
Early thymocyte development
where V(D)J recombination happens
T cell maturation
- positive selection
- negative selection
Positive selection
select thymocytes bearing receptors capable of binding self-MHC molecules with low affinity resulting in MHC restriction
Negative Selection
Selects against thymocytes bearing high-affinity receptors for self-MHC/ peptide complexes, resulting in self-tolerance
cTEC
cortical thymus epithelial cells express high levels of MHC class 1 and 2 on their surface -Cortex
DP learn MHC restriction in
the thymus
Three possible outcomes when T cells encounter set-peptide/MHC
- Cant bind (going to be deleted by neglect)
- Bind too strongly (self react, die by apoptosis)
- Bind just right (just right to CD4+ or CD8+)
Positive selection ensures
MHC restriction
Negative selection ensures
self-tolerance
