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On the dynamics of TCR:CD3 complex cell surface expression and downmodulation.
1Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38101, USA.
Immunity
|December 15, 2000
Summary
T-cell receptor (TCR) downmodulation occurs via intracellular retention and degradation, not increased internalization, following antigen binding. This process, driven by constitutive internalization, facilitates serial T cell activation.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- T-cell receptor (TCR) downmodulation after MHC:peptide complex ligation is crucial for T cell activation.
- Understanding the dynamics of TCR:CD3 complex expression is key to deciphering T cell signaling.
Purpose of the Study:
- To investigate the dynamics of TCR:CD3 cell surface expression in resting and activated T cells.
- To elucidate the mechanisms underlying TCR downmodulation upon antigen-specific ligation.
Main Methods:
- Analysis of TCR:CD3 complex cell surface expression dynamics.
- Investigation of internalization and recycling rates post-TCR ligation.
- Assessment of degradation pathways (lysosomes and proteasomes).
Main Results:
- The TCR:CD3 complex exhibits high stability with rapid internalization and recycling in resting T cells.
- TCR ligation does not increase the rate of internalization, despite causing downmodulation.
- TCR downmodulation results from intracellular retention and subsequent degradation of ligated complexes.
Conclusions:
- TCR downmodulation is primarily mediated by preventing the recycling of ligated complexes, not by inducing increased internalization.
- Constitutive internalization, rather than ligation-induced changes, drives serial TCR ligation events.
- These findings offer new insights into T cell activation regulation and immune response dynamics.