Newborn and child-like molecular signatures in older adults stem from TCR shifts across human lifespan.

CD8+ T cells provide robust antiviral immunity, but how epitope-specific T cells evolve across the human lifespan is unclear. Here we defined CD8+ T cell immunity directed at the prominent influenza epitope HLA-A*02:01-M158-66 (A2/M158) across four age groups at phenotypic, transcriptomic, clonal and functional levels. We identify a linear differentiation trajectory from newborns to children then adults, followed by divergence and a clonal reset in older adults. Gene profiles in older adults closely resemble those of newborns and children, despite being clonally distinct. Only child-derived and adult-derived A2/M158+CD8+ T cells had the potential to differentiate into highly cytotoxic epitope-specific CD8+ T cells, which was linked to highly functional public T cell receptor (TCR)αß signatures. Suboptimal TCRαß signatures in older adults led to less proliferation, polyfunctionality, avidity and recognition of peptide mutants, although displayed no signs of exhaustion. These data suggest that priming T cells at different stages of life might greatly affect CD8+ T cell responses toward viral infections.

Early Exacerbation Relapse is Increased in Patients with Asthma and Bronchiectasis (a Post hoc Analysis).

PURPOSE: Asthma is a common comorbidity in patients with bronchiectasis and has been shown to increase the risk of bronchiectasis exacerbations. This paper explores the impact of comorbid asthma on patients receiving intravenous antibiotic treatment for bronchiectasis exacerbations. METHODS: This was a post hoc analysis of the Meropenem randomised controlled trial of 90 patients that had intravenous antibiotic treatment for bronchiectasis exacerbations. The participants were split into two groups: group 1 (asthma and bronchiectasis) and group 2 (bronchiectasis). The authors assessed response to treatment and time to next exacerbation. RESULTS: There were 38 participants in group 1 and 34 participants in group 2. The groups were found to be comparable in terms of age, sex, and bronchiectasis severity (median (95% CI) group 1 and then group 2 data): age 64.0(59.3, 68.6) and 63.6(57.9, 69.4) years old, p = 0.8; 57.9% and 64.7% female, p = 0.6; Bronchiectasis Severity Index 11.1(9.8, 12.4) and 10.1(8.2, 12.0), p = 0.3. There was a similar response to treatment between the groups, but group 1 were found to relapse early by day 14, 31.6% in group 1 and 11.8% in group 2, p = 0.03. In the Cox proportional hazards model, asthma was the only independent risk factor for early relapse by day 14 (odds ratio (95% CI) 3.16 (1.02-9.79), p = 0.047). CONCLUSION: The clinical response to treatment was similar but patients with coexisting asthma were at increased risk of early relapse within 14 days of stopping intravenous antibiotic therapy. CLINICAL TRIAL REGISTRATION: NCT02047773.

HLA-B*27:05 alters immunodominance hierarchy of universal influenza-specific CD8+ T cells.

Seasonal influenza virus infections cause 290,000-650,000 deaths annually and severe morbidity in 3-5 million people. CD8+ T-cell responses towards virus-derived peptide/human leukocyte antigen (HLA) complexes provide the broadest cross-reactive immunity against human influenza viruses. Several universally-conserved CD8+ T-cell specificities that elicit prominent responses against human influenza A viruses (IAVs) have been identified. These include HLA-A*02:01-M158-66 (A2/M158), HLA-A*03:01-NP265-273, HLA-B*08:01-NP225-233, HLA-B*18:01-NP219-226, HLA-B*27:05-NP383-391 and HLA-B*57:01-NP199-207. The immunodominance hierarchies across these universal CD8+ T-cell epitopes were however unknown. Here, we probed immunodominance status of influenza-specific universal CD8+ T-cells in HLA-I heterozygote individuals expressing two or more universal HLAs for IAV. We found that while CD8+ T-cell responses directed towards A2/M158 were generally immunodominant, A2/M158+CD8+ T-cells were markedly diminished (subdominant) in HLA-A*02:01/B*27:05-expressing donors following ex vivo and in vitro analyses. A2/M158+CD8+ T-cells in non-HLA-B*27:05 individuals were immunodominant, contained optimal public TRBV19/TRAV27 TCRαß clonotypes and displayed highly polyfunctional and proliferative capacity, while A2/M158+CD8+ T cells in HLA-B*27:05-expressing donors were subdominant, with largely distinct TCRαß clonotypes and consequently markedly reduced avidity, proliferative and polyfunctional efficacy. Our data illustrate altered immunodominance patterns and immunodomination within human influenza-specific CD8+ T-cells. Accordingly, our work highlights the importance of understanding immunodominance hierarchies within individual donors across a spectrum of prominent virus-specific CD8+ T-cell specificities prior to designing T cell-directed vaccines and immunotherapies, for influenza and other infectious diseases.

Human Mucosal-Associated Invariant T Cells in Older Individuals Display Expanded TCRαß Clonotypes with Potent Antimicrobial Responses.

Mucosal-associated invariant T (MAIT) cells are important for immune responses against microbial infections. Although known to undergo marked numerical changes with age in humans, our understanding of how MAIT cells are altered during different phases across the human life span is largely unknown. Although also abundant in the tissues, our study focuses on MAIT cell analyses in blood. Across the human life span, we show that naive-like MAIT cells in umbilical cord blood switch to a central/effector memory-like profile that is sustained into older age. Whereas low-grade levels of plasma cytokine/chemokine were apparent in older donors (>65 y old), surprisingly, they did not correlate with the ex vivo MAIT hyperinflammatory cytokine profile observed in older adults. Removal of MAIT cells from older individuals and an aged environment resulted in the reversal of the baseline effector molecule profile comparable with MAIT cells from younger adults. An upregulated basal inflammatory profile accounted for reduced Escherichia coli-specific responses in aged MAIT cells compared with their young adult counterparts when fold change in expression levels of GzmB, CD107a, IFN-γ, and TNF was examined. However, the magnitude of antimicrobial MR1-dependent activation remained as potent and polyfunctional as with younger adults. Paired TCRαß analyses of MAIT cells revealed large clonal expansions in older adults and tissues that rivalled, remarkably, the TCRαß repertoire diversity of virus-specific CD8+ T cells. These data suggest that MAIT cells in older individuals, although associated with large clonal TCRαß expansions and increased baseline inflammatory potential, demonstrate plasticity and provide potent antimicrobial immunity.

Feasibility of shortening intravenous antibiotic therapy for bronchiectasis based on bacterial load: a proof-of-concept randomised controlled trial.

BACKGROUND: There is a lack of evidence to guide the duration of intravenous antibiotics for bronchiectasis exacerbations. AIMS: The aim of this study was to assess whether it is feasible, based on bacterial load, to shorten intravenous antibiotics during exacerbations and whether 14 days of treatment is superior. METHODS: We recruited participants requiring intravenous antibiotics for exacerbations. Participants were randomised into two groups: to receive antibiotics for 14 days (14-day group) or to have a shorter duration of treatment based on bacterial load (bacterial load-guided group (BLGG)). Bacterial load was checked on days 0, 7, 10, 14 and 21. If the bacterial load was <106 CFU·mL-1 on day 7 or day 10 in the BLGG, antibiotics were stopped the following day. RESULTS: A total of 47 participants were in the 14-day group and 43 were in the BLGG. 88% of participants in the BLGG were able to stop antibiotics by day 8 and potentially 81% of participants in the 14-day group could have stopped antibiotics at day 8. There was a nonsignificant trend for increased clinical improvement by day 21 in the 14-day group compared to the BLGG. However, overall group data showed the median (interquartile range) time to next exacerbation was 27.5 days (12.5-60 days) in the 14-day group and 60 days (18-110 days) in the in BLGG (p=0.0034). In a Cox proportional hazard model, participants in the 14-day group were more likely to experience exacerbations (HR 1.80, 95% CI 1.16-2.80, p=0.009) than those in the BLGG, and those with mild bronchiectasis were less likely to experience exacerbations than patients with more severe bronchiectasis (HR 0.359, 95% CI 0.13-0.99, p=0.048). CONCLUSIONS: Bacterial load-guided therapy is feasible in most exacerbations requiring intravenous antibiotics. There was a nonsignificant trend for increased clinical improvement by day 21 with 14 days of antibiotics compared with bacterial load-guided therapy but paradoxically there was a prolonged time to next exacerbation in the BLGG.

Human mucosal-associated invariant T cells contribute to antiviral influenza immunity via IL-18-dependent activation.

Mucosal-associated invariant T (MAIT) cells are innate-like T lymphocytes known to elicit potent immunity to a broad range of bacteria, mainly via the rapid production of inflammatory cytokines. Whether MAIT cells contribute to antiviral immunity is less clear. Here we asked whether MAIT cells produce cytokines/chemokines during severe human influenza virus infection. Our analysis in patients hospitalized with avian H7N9 influenza pneumonia showed that individuals who recovered had higher numbers of CD161(+)Vα7.2(+) MAIT cells in peripheral blood compared with those who succumbed, suggesting a possible protective role for this lymphocyte population. To understand the mechanism underlying MAIT cell activation during influenza, we cocultured influenza A virus (IAV)-infected human lung epithelial cells (A549) and human peripheral blood mononuclear cells in vitro, then assayed them by intracellular cytokine staining. Comparison of influenza-induced MAIT cell activation with the profile for natural killer cells (CD56(+)CD3(-)) showed robust up-regulation of IFNγ for both cell populations and granzyme B in MAIT cells, although the individual responses varied among healthy donors. However, in contrast to the requirement for cell-associated factors to promote NK cell activation, the induction of MAIT cell cytokine production was dependent on IL-18 (but not IL-12) production by IAV-exposed CD14(+) monocytes. Overall, this evidence for IAV activation via an indirect, IL-18-dependent mechanism indicates that MAIT cells are protective in influenza, and also possibly in any human disease process in which inflammation and IL-18 production occur.

Prostate cancer testing: a snapshot of the attitudes and practice of Australian general practitioners.

The role of the General Practitioner (GP) in testing for and managing men with prostate cancer (PCa) is significant. Very few studies have explored the attitudes and practices of Australian GPs in the context of the role of PCa testing. In this study, a 46-item web-based questionnaire was used to assess self-reported PCa testing attitudes and practices of GPs. This questionnaire was circulated to divisions of general practice and Medicare locals for further distribution to their GP members across Australia. GPs from all states and territories participated, and a total of 136 GPs completed the survey. Of the responding GPs, 57% always or usually offered PCa testing to asymptomatic men ≤ 70 years of age and 60% of GPs always or usually included a digital rectal examination (DRE). Many (80%) of the GPs stated that the current PCa testing guidelines were not clear. PCa testing was offered opportunistically by 56% while 39% offered testing at the patient's request. The results captured in this study represent a snapshot of GP attitudes and practices from across Australia. The results presented indicate a wide variation in the approaches to PCa testing in general practice across Australia, which in most part appear to be related to the lack of clarity of the current prostate cancer testing guidelines.

The Melbourne Consensus Statement on the early detection of prostate cancer.

Various conflicting guidelines and recommendations about prostate cancer screening and early detection have left both clinicians and their patients quite confused. At the Prostate Cancer World Congress held in Melbourne in August 2013, a multidisciplinary group of the world's leading experts in this area gathered together and generated this set of consensus statements to bring some clarity to this confusion. The five consensus statements provide clear guidance for clinicians counselling their patients about the early detection of prostate cancer.

Updates in digital shared care: Launching into the 21st century.

BACKGROUND: The recent Intergenerational Report (2023) highlighted that the Australian healthcare system will face increasing economic and logistical challenges, with projected growth in health spending due to an ageing population and an increasing number of chronic diseases. Shared care, a model emphasising collaboration between nursing and allied health, general practice and specialist care providers, has emerged as one solution. OBJECTIVE: This paper explores the contemporary shared care landscape in Australia, highlighting the digital transformation of healthcare, the adoption of eHealth technologies, and their impact on improving patient care coordination. DISCUSSION: The roles of shared electronic health records, secure electronic communication and consultation, electronic patient portals and telehealth in enhancing healthcare accessibility and management of chronic diseases are individually explored. Infrastructure for future inter-electronic medical record integrations are then discussed. Innovative care models combining novel technology and shared care hold promise for more efficient, patient­centric healthcare systems. Given Australia's unique healthcare challenges, it provides the ideal environment to lead the way in the digital transformation of shared care.

CD8+ T-cell responses towards conserved influenza B virus epitopes across anatomical sites and age.

Influenza B viruses (IBVs) cause substantive morbidity and mortality, and yet immunity towards IBVs remains understudied. CD8+ T-cells provide broadly cross-reactive immunity and alleviate disease severity by recognizing conserved epitopes. Despite the IBV burden, only 18 IBV-specific T-cell epitopes restricted by 5 HLAs have been identified currently. A broader array of conserved IBV T-cell epitopes is needed to develop effective cross-reactive T-cell based IBV vaccines. Here we identify 9 highly conserved IBV CD8+ T-cell epitopes restricted to HLA-B*07:02, HLA-B*08:01 and HLA-B*35:01. Memory IBV-specific tetramer+CD8+ T-cells are present within blood and tissues. Frequencies of IBV-specific CD8+ T-cells decline with age, but maintain a central memory phenotype. HLA-B*07:02 and HLA-B*08:01-restricted NP30-38 epitope-specific T-cells have distinct T-cell receptor repertoires. We provide structural basis for the IBV HLA-B*07:02-restricted NS1196-206 (11-mer) and HLA-B*07:02-restricted NP30-38 epitope presentation. Our study increases the number of IBV CD8+ T-cell epitopes, and defines IBV-specific CD8+ T-cells at cellular and molecular levels, across tissues and age.

Histamine-induced vasodilatation in the human forearm vasculature.

AIM: To investigate the mechanism of action of intra-arterial histamine in the human forearm vasculature. METHODS: Three studies were conducted to assess changes in forearm blood flow (FBF) using venous occlusion plethysmography in response to intra-brachial histamine. First, the dose-response was investigated by assessing FBF throughout a dose-escalating histamine infusion. Next, histamine was infused at a constant dose to assess acute tolerance. Finally, a four way, double-blind, randomized, placebo-controlled crossover study was conducted to assess FBF response to histamine in the presence of H1 - and H2 -receptor antagonists. Flare and itch were assessed in all studies. RESULTS: Histamine caused a dose-dependent increase in FBF, greatest with the highest dose (30 nmol min(-1) ) infused [mean (SEM) infused arm vs. control: 26.8 (5.3) vs. 2.6 ml min(-1) 100 ml(-1) ; P < 0.0001]. Dose-dependent flare and itch were demonstrated. Acute tolerance was not observed, with an increased FBF persisting throughout the infusion period. H2 -receptor antagonism significantly reduced FBF (mean (95% CI) difference from placebo at 30 nmol min(-1) histamine: -11.9 ml min(-1) 100 ml(-1) (-4.0, -19.8), P < 0.0001) and flare (mean (95% CI) difference from placebo: -403.7 cm(2) (-231.4, 576.0), P < 0.0001). No reduction in FBF or flare was observed in response to the H1 -receptor antagonist. Itch was unaffected by the treatments. Histamine did not stimulate vascular release of tissue plasminogen activator or von Willebrand factor. CONCLUSION: Histamine causes dose-dependent vasodilatation, flare and itch in the human forearm. H2 -receptors are important in this process. Our results support further exploration of combined H1 - and H2 -receptor antagonist therapy in acute allergic syndromes.

Best Current Practice and Research Priorities in Active Surveillance for Prostate Cancer-A Report of a Movember International Consensus Meeting.

BACKGROUND: Active surveillance (AS) is recommended for low-risk and some intermediate-risk prostate cancer. Uptake and practice of AS vary significantly across different settings, as does the experience of surveillance-from which tests are offered, and to the levels of psychological support. OBJECTIVE: To explore the current best practice and determine the most important research priorities in AS for prostate cancer. DESIGN, SETTING, AND PARTICIPANTS: A formal consensus process was followed, with an international expert panel of purposively sampled participants across a range of health care professionals and researchers, and those with lived experience of prostate cancer. Statements regarding the practice of AS and potential research priorities spanning the patient journey from surveillance to initiating treatment were developed. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Panel members scored each statement on a Likert scale. The group median score and measure of consensus were presented to participants prior to discussion and rescoring at panel meetings. Current best practice and future research priorities were identified, agreed upon, and finally ranked by panel members. RESULTS AND LIMITATIONS: There was consensus agreement that best practice includes the use of high-quality magnetic resonance imaging (MRI), which allows digital rectal examination (DRE) to be omitted, that repeat standard biopsy can be omitted when MRI and prostate-specific antigen (PSA) kinetics are stable, and that changes in PSA or DRE should prompt MRI ± biopsy rather than immediate active treatment. The highest ranked research priority was a dynamic, risk-adjusted AS approach, reducing testing for those at the least risk of progression. Improving the tests used in surveillance, ensuring equity of access and experience across different patients and settings, and improving information and communication between and within clinicians and patients were also high priorities. Limitations include the use of a limited number of panel members for practical reasons. CONCLUSIONS: The current best practice in AS includes the use of high-quality MRI to avoid DRE and as the first assessment for changes in PSA, with omission of repeat standard biopsy when PSA and MRI are stable. Development of a robust, dynamic, risk-adapted approach to surveillance is the highest research priority in AS for prostate cancer. PATIENT SUMMARY: A diverse group of experts in active surveillance, including a broad range of health care professionals and researchers and those with lived experience of prostate cancer, agreed that best practice includes the use of high-quality magnetic resonance imaging, which can allow digital rectal examination and some biopsies to be omitted. The highest research priority in active surveillance research was identified as the development of a dynamic, risk-adjusted approach.

Mechanisms for an effect of acetylcysteine on renal function after exposure to radio-graphic contrast material: study protocol.

BACKGROUND: Contrast-induced nephropathy is a common complication of contrast administration in patients with chronic kidney disease and diabetes. Its pathophysiology is not well understood; similarly the role of intravenous or oral acetylcysteine is unclear. Randomized controlled trials to date have been conducted without detailed knowledge of the effect of acetylcysteine on renal function. We are conducting a detailed mechanistic study of acetylcysteine on normal and impaired kidneys, both with and without contrast. This information would guide the choice of dose, route, and appropriate outcome measure for future clinical trials in patients with chronic kidney disease. METHODS/DESIGN: We designed a 4-part study. We have set up randomised controlled cross-over studies to assess the effect of intravenous (50 mg/kg/hr for 2 hrs before contrast exposure, then 20 mg/kg/hr for 5 hrs) or oral acetylcysteine (1200 mg twice daily for 2 days, starting the day before contrast exposure) on renal function in normal and diseased kidneys, and normal kidneys exposed to contrast. We have also set up a parallel-group randomized controlled trial to assess the effect of intravenous or oral acetylcysteine on patients with chronic kidney disease stage III undergoing elective coronary angiography. The primary outcome is change in renal blood flow; secondary outcomes include change in glomerular filtration rate, tubular function, urinary proteins, and oxidative balance. DISCUSSION: Contrast-induced nephropathy represents a significant source of hospital morbidity and mortality. Over the last ten years, acetylcysteine has been administered prior to contrast to reduce the risk of contrast-induced nephropathy. Randomized controlled trials, however, have not reliably demonstrated renoprotection; a recent large randomized controlled trial assessing a dose of oral acetylcysteine selected without mechanistic insight did not reduce the incidence of contrast-induced nephropathy. Our study should reveal the mechanism of effect of acetylcysteine on renal function and identify an appropriate route for future dose response studies and in time randomized controlled trials. TRIAL REGISTRATION: Clinical Trials.gov: NCT00558142; EudraCT: 2006-003509-18.

Non-targeted hepatitis C virus screening in acute care healthcare settings in the Southern Appalachian region.

Objectives: The objective of this study was to evaluate the performance of non-targeted hepatitis C virus (HCV) screening in emergency departments (EDs) and other healthcare settings in terms of patients identified with HCV infection and linked to HCV care. Methods: In the Southern Appalachian region of the United States, we developed non-targeted HCV screening and linkage-to-care programs in 10 institutions at different healthcare settings, including EDs, outpatient clinics, and inpatient units. Serum samples were tested for HCV antibodies, and if positive, reflexed to HCV ribonucleic acid (RNA) testing as a confirmatory test for active infection. Patients with positive RNA tests were contacted to link them to HCV care. Results: Between 2017 and 2019, among 195,152 patients screened for HCV infection, 16,529 (8.5%) were positive by antibody testing, 10,139 (5.2% of screened patients and 61.3% of patients positive by antibody test) were positive by RNA testing, and 5778 (3.0% of screened patients and 57.0% of patients positive by RNA test) were successfully linked to HCV care. Among 83,645 patients screened in EDs, 9060 (10.8%) were positive by HCV antibody, and 5243 (6.3%) were positive by RNA test. Among patients positive by RNA testing, linkage to care was lower for patients screened in the ED (44.1%) compared with outpatient clinics (67.6%) (P < 0.01) and inpatient units (50.9%) (P < 0.01). Conclusions: Non-targeted HCV screening in acute care settings can identify large numbers of people with HCV infection. To optimize the utility of these screening programs, future work is needed to develop best practices that consistently link these patients to HCV care.

Managing patients receiving new and unfamiliar cancer treatments: A qualitative study of general practitioners' experience.

BACKGROUND AND OBJECTIVES: As systemic cancer treatments increase in complexity, general practitioners (GPs) need access to reliable information to support patients on new and often unfamiliar treatments. The authors explored the experience of GPs in supporting patients receiving anticancer therapy, and the barriers and facilitators to the implementation of a new resource designed to support GPs in this role. METHOD: Semi-structured qualitative interviews were conducted with 15 GPs and oncology clinicians. Thematic analysis of interviews used inductive coding. RESULTS: Themes identified were GPs not feeling part of the team when looking after patients on cancer treatment, the role a new set of eviQ information resources could play in supporting GPs and barriers and facilitators to the implementation of these resources. DISCUSSION: GPs value reliable, published cancer treatment information, but it does not remove the need for individualised patient correspondence or the inclusion of the GP in the treating team.

Systems serology detects functionally distinct coronavirus antibody features in children and elderly.

The hallmarks of COVID-19 are higher pathogenicity and mortality in the elderly compared to children. Examining baseline SARS-CoV-2 cross-reactive immunological responses, induced by circulating human coronaviruses (hCoVs), is needed to understand such divergent clinical outcomes. Here we show analysis of coronavirus antibody responses of pre-pandemic healthy children (n = 89), adults (n = 98), elderly (n = 57), and COVID-19 patients (n = 50) by systems serology. Moderate levels of cross-reactive, but non-neutralizing, SARS-CoV-2 antibodies are detected in pre-pandemic healthy individuals. SARS-CoV-2 antigen-specific Fcγ receptor binding accurately distinguishes COVID-19 patients from healthy individuals, suggesting that SARS-CoV-2 infection induces qualitative changes to antibody Fc, enhancing Fcγ receptor engagement. Higher cross-reactive SARS-CoV-2 IgA and IgG are observed in healthy elderly, while healthy children display elevated SARS-CoV-2 IgM, suggesting that children have fewer hCoV exposures, resulting in less-experienced but more polyreactive humoral immunity. Age-dependent analysis of COVID-19 patients, confirms elevated class-switched antibodies in elderly, while children have stronger Fc responses which we demonstrate are functionally different. These insights will inform COVID-19 vaccination strategies, improved serological diagnostics and therapeutics.

Immune cellular networks underlying recovery from influenza virus infection in acute hospitalized patients.

How innate and adaptive immune responses work in concert to resolve influenza disease is yet to be fully investigated in one single study. Here, we utilize longitudinal samples from patients hospitalized with acute influenza to understand these immune responses. We report the dynamics of 18 important immune parameters, related to clinical, genetic and virological factors, in influenza patients across different severity levels. Influenza disease correlates with increases in IL-6/IL-8/MIP-1α/ß cytokines and lower antibody responses. Robust activation of circulating T follicular helper cells correlates with peak antibody-secreting cells and influenza heamaglutinin-specific memory B-cell numbers, which phenotypically differs from vaccination-induced B-cell responses. Numbers of influenza-specific CD8+ or CD4+ T cells increase early in disease and retain an activated phenotype during patient recovery. We report the characterisation of immune cellular networks underlying recovery from influenza infection which are highly relevant to other infectious diseases.

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

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.