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

Abstract

Background Although γδ 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 γδ T cells towards influenza viruses and defined influenza‐reactive γδ TCRs in the context of γδ‐TCRs across the human lifespan. Methods We performed 51Cr‐killing assay and single‐cell time‐lapse live video microscopy to define mechanisms underlying γδ T‐cell‐mediated killing of influenza‐infected targets. We assessed cytotoxic profiles of γδ T cells in influenza‐infected patients and IFN‐γ production towards influenza‐infected lung epithelial cells. Using single‐cell RT‐PCR, we characterised paired TCRγδ clonotypes for influenza‐reactive γδ T cells in comparison with TCRs from healthy neonates, adults, elderly donors and tissues. Results We provide the first visual evidence of γδ T‐cell‐mediated killing of influenza‐infected targets and show distinct features to those reported for CD8+ T cells. γδ T cells displayed poly‐cytotoxic profiles in influenza‐infected patients and produced IFN‐γ towards influenza‐infected cells. These IFN‐γ‐producing γδ T cells were skewed towards the γ9δ2 TCRs, particularly expressing the public GV9‐TCRγ, capable of pairing with numerous TCR‐δ chains, suggesting their significant role in γδ T‐cell immunity. Neonatal γδ T cells displayed extensive non‐overlapping TCRγδ repertoires, while adults had enriched γ9δ2‐pairings with diverse CDR3γδ regions. Conversely, the elderly showed distinct γδ‐pairings characterised by large clonal expansions, a profile also prominent in adult tissues. Conclusion Human TCRγδ repertoire is shaped by age, tissue compartmentalisation and the individual's history of infection, suggesting that these somewhat enigmatic γδ T cells indeed respond to antigen challenge.

Whole blood immunophenotyping uncovers immature neutrophil-to-VD2 T-cell ratio as an early prognostic marker for severe COVID-19

“…However, in the lungs, during chronic obstructive pulmonary disease, γδ T-cell counts have been reported to be significantly lower in induced sputum (IS) and bronchoalveolar lavage (BAL) but not in peripheral blood, suggesting unclear inflammatory mechanisms that could influence γδ T-cells counts in the periphery 46 . Interestingly, γδ T-cells, in particular VD2, are known to participate in influenza immune response 47 , and actively recruit and activate neutrophils to the site of infection or inflammation 48,49 . Activated, neutrophils have also been found to inhibit γδ T-cells functional capacity, promoting the resolution of inflammation 50,51 .…”

Human γδ TCR Repertoires in Health and Disease

“…Upon ageing, Kallemeijn and colleagues reported shrinking of the naïve γδ T cell population (CD45RA + CD27 + CD197 + ), while repertoire diversity was maintained [70,75]. Moreover, a tendency for a decreased Vγ9 usage and an increase of Vγ2-5 and Vγ8 chain usage in elderly individuals was shown for effector (CD45RA -CD45RO + CD27 -CD197 -) and central memory γδ T cells (CD45RA -CD45RO + CD27 + CD197 + ) [70,75], as well as a general reduction of paired Vγ9Vδ2 + TCRs in some individuals [66]. Furthermore, γδ TCR repertoires in healthy elderly individuals are characterized by large clonal expansions of particular non-Vγ9Vδ2 + clonotypes that could reflect the history of antigen challenge [66].…”

“…We might speculate that this simple rearrangement, and thus the length homogenization, coevolved with the pAg sensing ability of Vγ9Vδ2 + TCRs and the conserved binding of Vγ9 to BTN2A1 [18,21]. Thus, by retaining the binding capacity to BTN2A1, the Vγ9JP chain may pair with a multitude of Vδ2 + chains in the blood [66], creating a high TCR repertoire diversity of Vγ9Vδ2 + T cells. Further studies should address the effect of BTN2A1, and potentially other factors, to positively select Vγ9Vδ2 + T cells during thymic development.…”

“…In the case of Influenza A virus infections, Vγ9Vδ2 + T cells have been reported to kill infected cells and provide a major source of IFN-γ [90,91]. Recently, synapse formation and direct killing of H1N1/PR8-infected cells by γδ T cells have been shown ex vivo and Vγ9Vδ2 + T cells were described to be the main population of INF-γ producing γδ T cells [66,92].…”

“…However, knowledge of the human γδ TCR repertoire composition in healthy and diseased tissues remains fragmented. There is evidence that γδ TCR repertoires have an oligoclonal distribution in healthy liver, spleen, lymph node and lung [66,107]. An NGS analysis of intrahepatic Vδ2γδ T cells showed that CD69 + tissue-resident Vδ2 -T cells are characterized by unique TCR clones, while expanded TCR clones of liver-infiltrating Vδ2 -T cells are present in the blood of the respective donor, albeit with lower abundance.…”