Glossary of Immunology lecture 11 Development of T cells

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What are the 5 phases of T cell development
1. Arrival in the thymus and initial proliferation
2. Positive selection
3. Negative selection
4. Entery to the peripheral T cell pool
5. Terminal antigen stimulated differentiation into effector and memory cells
What is thymic stroma composed of
Cortical and medullary epithelial cells that play important roles in T cell development. Dendritic cells and macrophages also play important roles
What is the earliest stage of T cell development called
The double negative stage, because the cells do not express CD4 or CD8
Recombination of which TCR loci occurs first
Beta, Gamma and Delta
How many successive rearrangements are possible at the Beta chain locus
Two, because there are two cassettes of D and J segments
Expression of the pre-T cell receptor signals for what
Initiation of CD4 and CD8 co-receptor expression and the cells become double positive. Also signals for cessation of recombination at the Beta chain locus and for initiation of recombination at the alpha chain locus
What is positive selection
A process where those TCRs that can interact productively with self-MHC are selected
Where does positive selection of T cells occur
The thymic cortex, and is mediated by cortical epithelial cells
In the development of T cells, what does productive MHC interaction signal
Down regulation of either CD4 or CD8, and cessation of alpha chain rearrangment
What is negative selection
TCRs that interact too strongly with complexes of self MHC and peptide (autoreactive) are elimated from the pool of developing T cells
Where does negative selection of T cells (central tolerance) take place
Primarily at the cortico-medullary junction, and is mediated by dendritic cells and macrophages.
What are some T cell neoplasias
T cell acute lymphoblastic leukemia (T-ALL); Lymphoblastic lymphoma; Adult T cell leukemia/lymphoma (HTLV-1)

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