Human γδ T-cell receptor repertoire is shaped by influenza viruses, age and tissue compartmentalisation

Background Although gamma delta T cells comprise up to 10% of human peripheral blood T cells, questions remain regarding their role in disease states and T-cell receptor (TCR) clonal expansions. We dissected anti-viral functions of human gamma delta T cells towards influenza viruses and defined influenza-reactive gamma delta TCRs in the context of gamma delta-TCRs across the human lifespan. Methods We performed Cr-51-killing assay and single-cell time-lapse live video microscopy to define mechanisms underlying gamma delta T-cell-mediated killing of influenza-infected targets. We assessed cytotoxic profiles of gamma delta T cells in influenza-infected patients and IFN-gamma production towards influenza-infected lung epithelial cells. Using single-cell RT-PCR, we characterised paired TCR gamma delta clonotypes for influenza-reactive gamma delta T cells in comparison with TCRs from healthy neonates, adults, elderly donors and tissues. Results We provide the first visual evidence of gamma delta T-cell-mediated killing of influenza-infected targets and show distinct features to those reported for CD8(+) T cells. gamma delta T cells displayed poly-cytotoxic profiles in influenza-infected patients and produced IFN-gamma towards influenza-infected cells. These IFN-gamma-producing gamma delta T cells were skewed towards the gamma 9 delta 2 TCRs, particularly expressing the public GV9-TCR gamma, capable of pairing with numerous TCR-delta chains, suggesting their significant role in gamma delta T-cell immunity. Neonatal gamma delta T cells displayed extensive non-overlapping TCR gamma delta repertoires, while adults had enriched gamma 9 delta 2-pairings with diverse CDR3 gamma delta regions. Conversely, the elderly showed distinct gamma delta-pairings characterised by large clonal expansions, a profile also prominent in adult tissues. Conclusion Human TCR gamma delta repertoire is shaped by age, tissue compartmentalisation and the individual's history of infection, suggesting that these somewhat enigmatic gamma delta T cells indeed respond to antigen challenge.