Term
Role of the thymus in T cell development |
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Definition
-Required for T cell development
-Neonatal thymectomy (mouse)
-Nude mice
-DiGeorge Syndrome
-Shapes T cell repertoire
-Transplant experiments
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Term
What are thymocytes doing? |
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Definition
-Migrating
-Contacting stromal cells
-Changing phenotype
-Expressing TCRs
-Undergoing selection
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Term
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Definition
Subcapsular Region Immature CD3 CD4 CD8 double negative thymocytes
Cortex Immature CD 3 4 8 double Positive thymocytes
Corticomedullary Junction
Mature CD4+8- and CD4-8+ cells
Medulla |
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Term
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Definition
-Based on specificity of TCR
-Produces “central tolerance” to self antigens
-Produces T cell repertoire biased toward self MHC + peptide specificities
-Consists of 3 levels of selection
-Positive Selection
-Death by neglect
-Negative Selection
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Term
Thymic Selection (Postive Selection and Death by Neglect) |
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Definition
Positive Selection
Occurs at the CD4+/CD8+ stage
All cells with TCR affinity for self MHC + self peptides
Provides a “rescue signal” from apoptosis
Death by Neglect
-Occurs at the CD4+/CD8+ stage
-All cells with no TCR affinity for self MHC + self peptides
-Cells die by apoptosis
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Term
Thymic Selection (Negative Selection) |
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Definition
-Negative Selection
-Occurs at the CD4+/CD8+ stage and at the single positive (CD4 or CD8) stage
-All cells with high TCR affinity for self MHC + self peptides
-Results from the induction of apoptosis
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Term
Net Effect Of Thymic Selection |
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Definition
Net Effect of Selection
-By elimination of cells with no anti-self affinity (death by neglect) and those with high anti-self affinity (negative selection) we are left with T cells that have low affinity anti-self MHC + self peptide reactivity. Once mature, these will cross-react with with self MHC + a foreign peptide with high (activating) affinity.
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