30 Questions
What is the configuration of the TCR genes in the earliest cell entering the thymus?
Rearranged
What is the order of gene rearrangement if the γ chain genes rearrange successfully?
δ chain genes then β gene rearrangement
What is the role of recombination activation genes (RAGs) in T cells?
To activate the recombinase gene
What is the approximate number of different TCR structures that can be generated from αβ and γδ TCRs?
10^13
What is the process called when no further gene rearrangements occur after successful gene rearrangements?
Allelic exclusion
What happens if all the gene rearrangements are unsuccessful?
The second copy of genes on respective chromosomes will begin the rearrangement process
What is the function of RAG-1 and RAG-2 genes in the process of recombination?
To recognize specific DNA signal sequences
What is the difference between immuneoglobulin genes and genes encoding TCR?
Immunoglobulin genes do not undergo somatic mutation
Where do T lymphocytes develop?
In the thymus
What is the function of positive selection in the thymus?
To allow TCRs to recognize MHC molecules
What is the outcome of TCRs binding too strongly to p-MHC in the thymus?
Negative selection and elimination
What is the outcome of a defect in RAG-1 or RAG-2 genes?
Severe combined immunodeficiency (SCID)
What is the name of the cells that do not express either the CD4 or CD8 co-receptor?
Double-negative cells
At what stage do the cells decide to become δγ or αβ T cells?
At the double-negative stage
What percentage of thymocytes never become fully functional and die in the thymus?
96%-98%
What is the result of positive selection?
Down-regulation of RAG1 and RAG2 gene expression
What is the function of negative selection?
To remove T cells that express TCR with high reactivity to self components
What type of molecule is associated with the TCR β chain on the surface of pre-T cells?
Invariant pre-Tα molecule
What type of T-cells are MHC II restricted and recognize specific foreign peptides only when presented in association with specific MHC II molecules?
CD4 T-cells
Which type of T-cells produces cytokines of CMI and inflammation?
Th1 T-cells
What is the primary function of CD4 T-cells when recognizing antigen on the surface of APC?
Secreting cytokines
What is the term for the process by which T-cells that are unable to bind to MHC molecules are eliminated?
Negative selection
What is the primary function of CD8 T-cells?
Killing infected cells
What is the term for immature T-cells that express both CD4 and CD8?
Double-positive T-cells
What is the result of pre-TCR signaling in the development of cells expressing α and β as their TCR?
Further rearrangement of TCR β genes stops
What is the main function of positive selection in thymic selection?
Recognition of self-MHC and self-peptide
What is the composition of the pre-T cell receptor (pre-TCR)?
β chain and pre-Tα
What is the outcome of double positive cells that do not interact with MHC class I and II molecules?
They undergo apoptosis
What is the percentage of thymocytes that are double positive cells?
Over 80%
What is the role of thymic non-lymphoid cells in thymic selection?
Expressing MHC molecule plus peptide
Learn about the organization of human TCR genes and the order of TCR gene rearrangement, including the process of α and β chain genes rearrangement in the thymus and bone marrow. Understand how γ and δ chain genes rearrange and the implications on further gene rearrangement. Test your knowledge of TCR gene organization and rearrangement!
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