Attenuator riboswitch (Leader sequence) contains two major check-points in region 1

1. UGG codons on position 10, 11

2. A stop codon UGA between Region 1 and 2

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#Unit 4. Cell Communication and Cell Signaling

Allelic exclusion

Most T cells fully rearrange and express a TCR chain from only one of their two TCR alleles

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#Unit 4. Cell Communication and Cell Signaling

Thymic selection

The most distinctive property of the mature T cells is that they recognize only foreign antigen combined with self-MHC molecules.

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#Unit 4. Cell Communication and Cell Signaling

Two distinct selection processes are required:

 • Positive selection, which selects for those thymocytes bearing receptors capable of binding self-MHC molecules, resulting in MHC restriction

• Negative selection, which selects against thymocytes bearing high-affinity receptors for self-MHC/peptide complexes, resulting in self-tolerance.

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#Unit 4. Cell Communication and Cell Signaling

T-cell education

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Relationship between TCR affinity and selection

TLS Online TPP Program

#Id: 1893

#Unit 4. Cell Communication and Cell Signaling

Superantigens

Viral or bacterial proteins that bind simultaneously to the Vβ domain of a T-cell receptor and to the α chain of a Class II MHC molecule