{
  "abstract": "Introduction and Objectives CD11b and CD11c are key components of the integrins Mac-1 and CR4, respectively. During inflammation, CD11b and CD11c are upregulated on the cell surface of neutrophils. Previous reports suggest both CD11b and CD11c are involved in neutrophil extravasation, but there are few data regarding human neutrophils. We hypothesised that the roles of CD11b and CD11c may vary between the pulmonary and systemic circulations.Methods CD34+ haematopoietic stem cells (HPSCs) were isolated from human apheresis cones by magnetic selection and expanded. Cas9-gRNP complexes were nucleofected into the HSPCs resulting in >90% knockdown of ITGAM and ITGAX at genomic and protein levels. After subsequent directed differentiation into neutrophils in the presence of recombinant human granulocyte colony stimulating factor, CD11bKO (N = 7), CD11cKO (N = 7), and donor-matched non-targeting (scrambled) control cells (SCR) were flowed over confluent TNF-stimulated pulmonary and dermal (systemic) microvascular endothelial monolayers. Phase-contrast microscopy timelapse images were obtained, and the phases of extravasation (rolling, adhesion, crawling and transmigration) were quantified using ImageJ, with crawling mechanics assessed using TrackMate.Results Compared to SCR control neutrophils, fewer CD11bKO neutrophils engaged in rolling (p = 0.047) and crawling (p = 0.031) when interacting with pulmonary, but not systemic, microvascular endothelial cells. CD11bKO neutrophils also displayed increased crawling linearity (p = 0.031) when interacting with pulmonary microvascular endothelial cells.No changes in neutrophil-endothelial interactions were observed with CD11cKO cells, when were flowed across both pulmonary and systemic microvascular endothelial cells. Similarly, no difference in crawling mechanics was seen with knockout of CD11c.Conclusion We have shown for the first time in human neutrophils that CD11b mediates crawling and rolling across pulmonary, but not systemic, microvascular endothelial cells, and that CD11c is dispensable for human neutrophil extravasation in the pulmonary and systemic circulations. Our data supports the hypothesis that there is variation across endothelial beds in the requirement for integrins during human neutrophil extravasation.",
  "authors": [
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "DTH Nguyen"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "IA Sava"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "Z Zhang"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "E Vozza"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "L Flower"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "N Farahi"
    },
    {
      "affiliations": [
        "University of Cambridge, Cambridge, UK"
      ],
      "name": "C Summers"
    }
  ],
  "title": "S166 Differential roles of the integrins CD11b and CD11c in human neutrophil extravasation across pulmonary and systemic endothelium",
  "uid": "c8f17185-388d-541b-94eb-3cf312d7caea"
}