{
  "abstract": "Introduction Severe asthma is typically characterized by high levels of eosinophilic inflammation. Evidence from animal models and studies of mild-moderate asthma suggest there may be different inflammatory profiles of blood and bronchoalveolar lavage (BAL) eosinophils, but these differences remain poorly defined. Whether such differences exist in severe eosinophilic asthma (SEA) is unknown, however an understanding of such phenotypic and functional characteristics may be clinically relevant and inform biologic treatment choice.Methods Paired peripheral blood and BAL samples were collected from 11 patients with SEA. CyTOF was performed on whole blood and BAL cells. Eosinophils were gated based on CD66b, CD294 and CD125 expression and then further subtyped based on functional and phenotypical markers. Following UMAP visualisation ( figure 1), mass cytometry data underwent FlowSOM clustering to identify phenotypically distinct subpopulations. Expression levels of lineage and functional markers were compared between blood and BAL eosinophils. Relative cluster distributions were assessed using compositional analysis, and differential expression was statistically evaluated.Results UMAP visualization revealed distinct clustering patterns of blood and BAL eosinophils, indicating phenotypic divergence (p<0.001). FlowSOM clustering identified 6 main metaclusters, 4 of which were enriched in BAL eosinophils, and 2 in blood eosinophils. Heatmap analysis highlighted differential expression of CD196 across the clusters of BAL eosinophils. Eosinophils with low CD196 expression had high IL-13 expression, suggesting a more migratory phenotype. The 2 main metaclusters of blood eosinophils were differentiated by CD45RA expression or high TSLPR expression. Additionally, the blood microenvironment was different to the BAL, with significantly higher levels of CCL11, CCL26, IP-10, MCP-4 and MIP3a (all p<0.05), whereas BAL showed significantly higher levels of GROa(p=0.03) and CXCL8(p=0.01).Abstract S104 Figure 1Conclusion Simultaneous measurements of BAL and blood eosinophils from patients with SEA demonstrate specific compartment related differences in marker expression, with multiple subgroups of eosinophils present in each compartment. How these differences relate to baseline clinical features and response to anti-IL5R therapy is an area of ongoing investigation.",
  "authors": [
    {
      "affiliations": [
        "Guys Severe Asthma Centre Guys and St Thomas NHS Trust, London, UK"
      ],
      "name": "J Gates"
    },
    {
      "affiliations": [
        "School of Immunology and Microbial Sciences Kings College London, London, UK"
      ],
      "name": "P Khooshemehri"
    },
    {
      "affiliations": [
        "School of Immunology and Microbial Sciences Kings College London, London, UK"
      ],
      "name": "S Cass"
    },
    {
      "affiliations": [
        "School of Immunology and Microbial Sciences Kings College London, London, UK"
      ],
      "name": "J Baker"
    },
    {
      "affiliations": [
        "Guys Severe Asthma Centre Guys and St Thomas NHS Trust, London, UK"
      ],
      "name": "A del Rosario"
    },
    {
      "affiliations": [
        "School of Immunology and Microbial Sciences Kings College London, London, UK"
      ],
      "name": "V Kanabar"
    },
    {
      "affiliations": [
        "Guys Severe Asthma Centre Guys and St Thomas NHS Trust, London, UK"
      ],
      "name": "J Dhariwal"
    },
    {
      "affiliations": [
        "Guys Severe Asthma Centre Guys and St Thomas NHS Trust, London, UK"
      ],
      "name": "AM Nanzer"
    },
    {
      "affiliations": [
        "School of Immunology and Microbial Sciences Kings College London, London, UK"
      ],
      "name": "RT Martinez Nunez"
    },
    {
      "affiliations": [
        "Guys Severe Asthma Centre Guys and St Thomas NHS Trust, London, UK"
      ],
      "name": "DJ Jackson"
    }
  ],
  "title": "S104 Blood and airway eosinophils in severe eosinophilic asthma are phenotypically and functionally distinct",
  "uid": "dc2f9a73-ded4-5d37-9d5a-e88070fb91ae"
}