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Transient alteration of T cell fine specificity by a strong primary stimulus correlates with T cell receptor
1Department of Immunology and Howard Hughes Medical Institute, University of Washington, Seattle 98195-7370, USA.
Abstract:
P14 mice expressing a transgenic TCR specific for the lymphocytic choriomeningitis virus glycoprotein p33 epitope were used to study the induction of CTL effector activity by a variety of ligands. Surprisingly, p33 variants which are weaker agonists for the P14 TCR than the wild-type p33 peptide were able to induce more potent effectors with a broader range of cytolytic specificity. Similarly, low concentrations of p33 were more effective than higher concentrations. These results correlated with no or only moderate TCR down-regulation by variants of p33 and low p33 concentrations. This phenotype observed after 18 h of culture was transient as progressive restoration of reactivity was observed at 42 or 66 h in the cultures stimulated with high p33 concentrations and this correlated with recovery of TCR surface levels. TCR down-regulation was blocked by src family kinase inhibitors. These findings indicate that the specificity of a T cell can be fine-tuned by the nature of the primary stimulus correlating with surface TCR level and imply an important role for src family kinases in the differential regulation of surface TCR levels upon TCR engagement by different ligand/MHC complexes.
Insights
Weaker T cell receptor (TCR) agonists and lower peptide concentrations induced stronger T cell responses. This suggests TCR signaling fine-tuning by ligand quality and quantity, involving src family kinases.
Area of Science:
- Immunology
- Molecular Biology
- T cell signaling
Background:
- T cell receptor (TCR) signaling is crucial for adaptive immunity.
- The magnitude and specificity of T cell responses are influenced by ligand interactions.
- TCR down-regulation is a known mechanism modulating T cell activation.
Purpose of the Study:
- To investigate how different T cell receptor (TCR) ligands modulate cytotoxic T lymphocyte (CTL) effector activity.
- To explore the role of TCR down-regulation in T cell responses.
- To identify signaling pathways involved in differential TCR regulation.
Main Methods:
- Utilized P14 mice with transgenic TCRs specific for lymphocytic choriomeningitis virus (LCMV) p33 epitope.
- Compared CTL effector activity induced by wild-type p33 and its variants with varying agonist strengths.
- Assessed TCR surface levels and blocked src family kinases to analyze signaling pathways.
Main Results:
- Weaker TCR agonists and lower peptide concentrations induced more potent CTL effectors with broader specificity.
- These conditions correlated with minimal TCR down-regulation.
- Src family kinase inhibition blocked TCR down-regulation, and T cell reactivity recovered over time with high peptide concentrations.
Conclusions:
- T cell specificity can be fine-tuned by the nature and concentration of the primary stimulus.
- Surface TCR levels, regulated by src family kinases, play a key role in differential T cell responses.
- Ligand-induced TCR down-regulation is a transient mechanism impacting T cell effector function.