chapter 8 Flashcards
VERY early thymocyte development occurs in the _____________________
bone marrow
Describe T cell development starting from the bone marrow:
-T-cell precursors begin their travel through the thymus at the cortex
-T-cells that survive selection migrate into the medulla
What happens during the positive/negative selection stages?
the cell becomes a single positive CD4+ or CD8+
Recombination of TCR gene segments also occurs in the DN stages, yielding either _______________T cell
an αβ or a γδ
What is the name of the receptor that commits cells to the T cell lineage?
notch
During which stage does TCR rearrangement begin in?
DN2
Which receptor rearrangements are one of the first to take place?
TCRβ
What is the process of Beta selection that double negative thymocytes undergo?
-A successfully produced β chain is paired with the pre-Tα chain
-After β-selection has occurred, thymocytes are at the DP stage of development
-Pos./neg. selection occurs, yielding mature SP T cell
Double positive thymocytes make up what percentage of thymic cells?
80%
What does positive selection select for?
selects thymocytes bearing receptors capable of binding self-MHC molecules, resulting MHC restriction
What does negative selection select for?
selects against thymocytes bearing high-affinity receptors for self-MHC/self-peptide complexes, resulting in self-tolerance
Most cells (95%) fail positive selection and fail to receive what?
needed survival signals
How does positive selection ensure MHC restriction?
-most cells die by neglect before they could reach a negative selection stage
-those that can bind MHCs shift from DP to SP
Where do thymocytes learn MHC restriction
the thymus
How does negative selection ensure self-tolerance?
-clonal deletion
-clonal arrest
-clonal anergy
-clonal editing
