T-cell-receptor affinity and thymocyte positive selection

Article Abstract:

The major histocompatibility complex- bound peptide that cause positive selection of thymocytes and rescue them from cell death have a lower binding affinity for T-cell-receptors than complexes that cause negative selection. The complexes causing positive selection also dissociate faster. Surface plasmon resonance studies show that an equilibrium dissociation constant (K(sub d)) between 20-50 micro-M causes positive selection while a K(sub d) of 10 micro-M or less causes negative selection.

Analysis, Major histocompatibility complex, Cooperative binding (Biochemistry)

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Thymic selection threshold defined by compartmentalization of Ras/MAPK signalling

Article Abstract:

Thymocyte selection threshold is elucidated by identifying the ligands that define an extremely narrow gap spanning the threshold that distinguishes positive from negative selection. The results have shown that a small increase in ligand affinity for the T-cell antigen receptor has led to a marked change in the activation and subcellular localization of Ras and mitogen-activated protein kinase (MAPK) signalling intermediates and the induction of negative selection.

Science & research, Protein kinases, T cells, Immune response

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Enterotoxin residues determining T-cell receptor V-beta binding specificity

Article Abstract:

Exactly how the staphylococcal enterotoxins function as superantigens by attaching to the T-cell antigen receptors (TCR) and the major histocompatibility complex class II molecules has become clearer due to experiments using hybrid molecules. These experiments showed that amino-acid residues at the carboxyl terminus allow the enterotoxins to focus on different TCR beta-chain binding sites. The enterotoxins' crystalline morphology also aids in reacting to TCR.

Enterotoxins, Antigens

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