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T Cell Activation and Clonal Selection

T Cell Activation and Clonal Selection

T cells are integral to our adaptive immune system, recognizing and effectively responding to foreign antigens. T cell activation and clonal selection are pivotal in orchestrating this immune response. This article elucidates these mechanisms, detailing the roles of cluster of differentiation (CD) markers, major histocompatibility complex (MHC) molecules, costimulatory signals, and the process of clonal selection.
Naive T cells that have not yet encountered an antigen express two primary CD...

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A TIRF Microscopy Technique for Real-time, Simultaneous Imaging of the TCR and its Associated Signaling Proteins

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Published on: March 22, 2012

A permissive geometry model for TCR-CD3 activation.

Susana Minguet¹, Wolfgang W A Schamel

¹Max Planck Institute for Immunobiology and University of Freiburg, Stübeweg 51, 79108 Freiburg, Germany.

Trends in Biochemical Sciences

|January 19, 2008

Summary

The T cell receptor (TCR-CD3) complex uses antigen geometry to initiate immune responses. Dimeric antigens bind two receptors, causing a scissor-like movement that activates intracellular signaling.

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Area of Science:

Immunology
Molecular Biology
Structural Biology

Background:

The T cell receptor (TCR-CD3) complex is crucial for initiating adaptive immune responses.
Its activation mechanism by antigens remains incompletely understood.
The TCR-CD3 complex comprises eight transmembrane subunits, making it highly intricate.

Purpose of the Study:

To elucidate the mechanism by which antigen binding to the TCR-CD3 complex initiates intracellular signaling cascades.
To present the permissive geometry model for TCR-CD3 activation.

Main Methods:

The study proposes a model based on the geometric constraints of antigen binding.
Analysis of the proposed conformational changes in the TCR-CD3 complex upon antigen engagement.

Main Results:

A dimeric antigen simultaneously binding to two TCR-CD3 receptors imposes its geometry.
This binding induces rotation of TCRalphabeta subunits and displacement of CD3 ectodomains.
A scissor-like movement of CD3 dimers exposes cytoplasmic tails, enabling signaling protein interaction.

Conclusions:

The permissive geometry model explains how antigen binding triggers TCR-CD3 signaling.
This mechanism involves specific geometric interactions between dimeric antigens and the receptor complex.
Understanding this process is key to deciphering immune response initiation.