The human γδ T cell repertoire is shaped by age, tissue compartmentalization and viral exposure

Abstract γδ T cells can provide immunity against foreign pathogens and internal tissue malignancies. Despite numerous studies in mice, the potential role of γδ T cells in human viral infections and their TCR profiles are understudied, especially at different tissue locations. We utilised a single-cell multiplex-nested-RT-PCR to dissect the TCRγδ repertoire (n=372 γδ pairs) in healthy individuals across three major age groups (neonates, adults and elderly donors) in peripheral blood and tissues (spleen, lymph node and lungs). Neonatal γδTCRs display diverse TCRγδ repertoires, while adults show an enrichment of γ9δ2 TCRs with diverse CDR3 regions. Strikingly, elderly donors displayed distinct TCRγδ profiles with large clonal CDR3 expansion. Tissue-associated TCRγδ usage differs markedly from γ9δ2 cells that dominate the adult peripheral blood with more restricted CDR3 regions. Using our established in vitro co-culture assay of influenza virus infection in lung epithelial cells, we found that human γδ T cells respond to influenza infection by IFN-γ production and enrichment of γ9δ2 T cells. Our findings further support the role of monocytes and IL-15 in γδ T cell activation after influenza infection. Our study provides novel insights into the composition and diversity of TCRγδ repertoires and demonstrates how human γδ TCRs are shaped by the age, tissue compartmentalization and viruses. Our findings have future implications for immunotherapies involving γδ T cells in patients across different ages.