{
  "abstract": "Background Biliary tract cancer (BTC) remains therapeutically challenging with poor survival outcomes despite systemic therapies achieving complete responses in only 2–5% of patients. γδ T cell-based adoptive cell therapy represents a promising strategy due to MHC-independent activation. γδ T cells are activated through direct engagement of butyrophilin (BTN) family molecules. Conversely, non-classical HLA class I molecules, particularly HLA-E, function as ligands for inhibitory receptors (NKG2A) expressed on γδ T cells, delivering suppressive signals that dampen anti-tumour immunity (15). The balance between activating BTN-mediated signals and inhibitory HLA-E/NKG2A interactions critically determines γδ T cell anti-tumour potential. The characteristics of tumour-infiltrating γδ T cells and their activity and inhibitory interactions in BTC remain unexplored.Methods Single-cell RNA-sequencing data from 19 BTC tumour samples across three independent Gene Expression Omnibus (GEO) datasets were analysed using Seurat to characterise γδ T cell infiltration and expression of regulatory molecules. Classical (HLA-A/B/C) and non-classical (HLA-E/F/G) MHC-I molecules, butyrophilin (BTN) family members, intercellular adhesion molecules (ICAM), and NKG2A checkpoint receptors were quantified using marker-based definitions and dot plot visualisation.Results γδ T cells comprised 0 - 4.9% of all cells ( figure 1) present in the BTC tumour samples evaluated (mean: 1.3%). Expression of BTN2A1, BTN2A2, BTN3A1, BTN3A2, ICAM1 were noted in all the tissue samples, supporting Vγ9Vδ2 T cell activation potential. Classical HLA class I expression was generally preserved (70-90% of cells), though inter-sample variability was noted. HLA-E was overexpressed (60-95.7% of cells expressing HLA-E), whilst HLA-G was minimal. Around 30% of NK cells and γδ T cells exhibited NKG2A positivity with high expression (log2 expression >2).Conclusions Based on the presence of regulatory molecules such as BTN and ICAM, Vγ9Vδ2 T cell-based adoptive cell therapy appears to have potential. The combination of elevated HLA-E expression with high γδ T cell NKG2A positivity establishes a potent inhibitory checkpoint axis in BTC. These findings support the rationale of investigating anti-NKG2A blockade combined with γδ T cell-based adoptive therapy as a novel therapeutic strategy.Abstract P77 Figure 1γδ T Cell infiltration patterns in BTC tumour microenvironment (TME) from 3 different GEO datasets. A: Harmony integration of multi-dataset BTC scRNA-seq data.B: Marker gene expression across clusters – cell lineage-specific characterisation (Clusters 4, 5, 6, 29, 31, 32 resemble γδ T cells). C: UMAP by cell clustering of Harmony integrated BTC scRNA-seq Data. D: UMAP plot of γδ T cells and NK cells.",
  "authors": [
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Saikat Mandal"
    },
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Stuart Astbury"
    },
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Jane Grove"
    },
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Judith Ramage"
    },
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Andrew Jackson"
    },
    {
      "affiliations": [
        "University of Nottingham, Nottingham, United Kingdom"
      ],
      "name": "Guruprasad Aithal"
    }
  ],
  "title": "P77 Single-cell transcriptomic analysis reveals γδ t cell infiltration and presence of immune regulatory molecules in biliary tract cancer microenvironment",
  "uid": "c635acd7-6f91-5d57-9208-d36f64808f04"
}