Two Step Selection for Bias in β Chain V-J Pairing

Area of Science:

• Immunology
• Molecular Biology
• T cell development

Background:

• T cell receptor (TCR) beta chain rearrangement is a critical process for T cell maturation.
• This process involves the joining of V, D, and J gene segments in a specific order.
• Previous understanding suggested random V gene usage based on individual gene frequencies.

Purpose of the Study:

• To investigate the frequency and patterns of V gene segment combinations during TCR beta chain rearrangement.
• To identify potential structural mechanisms influencing V gene pairing.
• To determine if these biases occur before or after thymic selection.

Main Methods:

• Analysis of V gene segment usage and combinations in human and mouse T cell populations.
• Comparison of observed V gene pairing frequencies with expected frequencies based on gene usage.
• Correlation analysis of V gene usage with molecular properties (Molecular Weight, Isoelectric Point).
• Examination of V gene pairing in thymocytes at different developmental stages.

Main Results:

• Observed V gene combinations deviate significantly from expected frequencies in both functional and non-functional rearrangements.
• Preferred V gene pairings are conserved across human donors and mouse samples, suggesting a common structural basis.
• V gene usage correlates with Molecular Weight and Isoelectric Point in functional T cell clones.
• Similar V gene pairing biases are present in Double Positive thymocytes, preceding thymic selection.

Conclusions:

• A pre-thymic structural checkpoint influences TCR beta chain V gene selection.
• This structural selection mechanism operates independently of antigen-driven peripheral selection.
• Understanding these biases is crucial for distinguishing normal from aberrant T cell development and for engineering TCRs.