Head and neck cancer (HNC) exhibits a strongly immunosuppressive tumour environment. This study investigated whether plasma small extracellular vesicles (sEVs) from HNC patients alter T-cell phenotypes and contribute to systemic immune dysfunction. Plasma sEVs were isolated by size-exclusion chromatography (SEC) from HNC patients (N = 50), recovered patients with no evident disease (NED, N = 20), and healthy donors (HD, N = 22). HNC-derived sEVs inhibited CD4+ and CD8+ T-cell function, promoted CD8+ T-cell apoptosis in vitro, and these effects correlated with disease progression. Plasma sEVs enhanced conversion of ATP to AMP and modulated ectonucleotidase expression, implicating the adenosinergic pathway (CD39/CD73). Immune-checkpoint profiling revealed complex, subset-specific changes: CD4+ T cells showed increased TIGIT and CTLA-4 but decreased BTLA, PD‑1, and LAG‑3, while CD8+ T cells displayed downregulation of both inhibitory and stimulatory checkpoints. PD‑1 blockade did not fully prevent sEV-mediated suppression. The authors conclude that plasma sEVs contribute to systemic immune modulation in HNC and warrant further study for their relevance to immunotherapy.
Head and neck cancers rank among the top ten cancer types worldwide and are frequently diagnosed at advanced stages, contributing to poor prognosis. A hallmark of HNC is the immunosuppressive tumour microenvironment, with upregulated inhibitory immune checkpoints such as PD‑1/PD‑L1 and CTLA‑4 that blunt antitumour T-cell responses. Although immune checkpoint inhibitors (ICIs) have improved outcomes for some patients, many do not respond, suggesting additional immunoregulatory mechanisms operate beyond canonical checkpoint pathways.
Tumour-derived extracellular vesicles, including sEVs, are released into body fluids and have documented immunomodulatory roles. Prior studies in HNC reported that plasma and saliva sEVs suppress lymphocyte function, reduce NK cell cytotoxicity, skew macrophage polarization, and alter dendritic cell antigen processing. sEVs can carry immunosuppressive proteins such as PD‑L1/PD‑L2 and can engage the adenosinergic pathway through ectonucleotidases, supporting an immunosuppressive milieu. Some TEV effects may occur via direct surface signalling rather than uptake by recipient cells.
The present study aimed to characterise plasma sEVs from HNC patients, assess their influence on CD4+ and CD8+ T-cell function and apoptosis, measure changes in ectonucleotidase activity and purinergic metabolism, and profile alterations in immune-checkpoint expression. Interactions between sEV-mediated effects and PD‑1 blockade were also investigated to evaluate relevance for immunotherapy.
Venous blood was collected into citrate monovettes from HNC patients (N = 50), recovered patients with no evident disease (NED, N = 20) and healthy donors (HD, N = 22) at the University Hospital Mannheim between 2019 and 2023. The overall sample size was determined by availability. Participant consent was obtained and the study was approved by the Ethics Committee II of the University of Heidelberg (protocol numbers reported in the source). For plasma preparation, blood was centrifuged at 2000 × g for 10 minutes at room temperature, aliquoted, and stored at −80 °C.
Plasma sEVs were isolated by size-exclusion chromatography (SEC). Pre-clearing steps included centrifugation at 2000 × g for 10 minutes followed by 14,000 × g for 30 minutes at 4 °C and filtration through a 0.22 µm filter. SEC columns were prepared using 10 mL cross-linked Sepharose CL-2B packed into Econo-Pac columns; 1 mL of pre-cleared plasma was applied and the fourth 1 mL PBS eluate fraction was collected as the sEV-containing fraction, following previously described protocols.
Transmission electron microscopy (TEM) was performed on sEV preparations from at least two HNC patients as part of morphological characterisation. The provided excerpt ends at the initial TEM mention; additional details on TEM findings, nanoparticle tracking, protein markers, or other characterisation metrics were not reported in the available source text.
Key findings reported in the abstract and background sections were:
Plasma sEVs from HNC patients inhibited functions of both CD4+ and CD8+ T cells in vitro and promoted apoptosis of CD8+ T cells. These functional impairments correlated with clinical disease progression.
sEVs enhanced conversion of ATP to AMP and modulated expression of ectonucleotidases, consistent with activation of the adenosinergic pathway mediated by CD39 and CD73, which can generate immunosuppressive adenosine.
Immune-checkpoint profiling of T-cell subsets after exposure to patient-derived sEVs showed complex, subset-specific changes: CD4+ T cells had increased TIGIT and CTLA‑4 but decreased BTLA, PD‑1, and LAG‑3; CD8+ T cells exhibited downregulation of both inhibitory and stimulatory checkpoint molecules.
Pharmacological PD‑1 blockade (PD‑1 inhibition) did not fully abrogate the suppressive influence of plasma sEVs on T cells, indicating multiple mechanisms contribute to sEV-mediated immune suppression beyond PD‑1/PD‑L1 interactions.
Detailed numerical results, effect sizes, statistics, subgroup analyses, and complete characterisation data were not included in the supplied excerpt.
The reported data support the concept that circulating sEVs from HNC patients exert systemic immunomodulatory effects by inducing dysfunctional T-cell phenotypes, promoting CD8+ apoptosis, and engaging purinergic/adenosinergic pathways. The observed modulation of immune-checkpoint expression on T-cell subsets is complex and not limited to conventional PD‑1/PD‑L1 interactions; this complexity may help explain partial resistance to PD‑1 blockade in some patients.
The authors propose that plasma-derived sEVs could be relevant for immunotherapeutic strategies and biomarker development in HNC; however, the excerpted article portion did not provide full datasets or methodological details for all experiments. Further comprehensive analyses are needed to define the mechanistic drivers within sEV cargo, quantify clinical correlations, and test whether targeting sEV production, release, or specific cargo can modify patient responses to ICIs.
Note: The source excerpt provided here did not include full experimental results, extended methods for several assays, detailed TEM characterisation outputs, or complete statistical reporting. Those details were not reported in the supplied text and would require consultation of the full published article.