Gammadelta T cells - innate immune lymphocytes?

Area of Science:

• Immunology
• T-cell biology
• Molecular recognition

Background:

• The antigen recognition determinants of gammadelta T-cell receptors (TCRs) remain largely unknown.
• Gammadelta TCRs exhibit high complementarity-determining region 3 (CDR3) diversity via VDJ recombination, yet reactivity often correlates with V gene usage, questioning the role of rearrangement in antigen specificity.
• Existing knowledge suggests a gap in understanding how gammadelta TCRs achieve specific antigen recognition despite their diverse repertoire.

Purpose of the Study:

• To investigate the role of CDR3 regions in determining the antigen specificities of gammadelta TCRs.
• To identify ligands recognized by human phosphoantigen-reactive gammadelta T cells.
• To elucidate the structural basis of gammadelta TCR-ligand interactions.

Main Methods:

• Analysis of CDR3 regions in T10- and T22-reactive gammadelta TCRs.
• Identification of a surface protein complex serving as a ligand for specific gammadelta T cells.
• Co-crystallization of a gammadelta TCR with its identified ligand.

Main Results:

• The CDR3 regions of gammadelta TCRs were confirmed to dictate antigen specificities for T10 and T22 recognition.
• A specific surface protein complex was identified as the ligand for human phosphoantigen-reactive gammadelta T cells.
• The first co-crystal structure of a gammadelta TCR bound to its ligand was successfully determined.

Conclusions:

• Recent advances demonstrate that CDR3 diversity and specific ligand interactions are key determinants of gammadelta TCR antigen recognition.
• The identification of ligands and structural data provide critical insights into the specificity of gammadelta T cells.
• These findings necessitate a re-evaluation of gammadelta T-cell antigen recognition mechanisms.