A novel real time imaging platform to quantify macrophage phagocytosis

Research output: Contribution to journalArticle

Authors

  • Theodore S Kapellos
  • Lewis Taylor
  • Heyne Lee
  • Sally A Cowley
  • William S James
  • David R Greaves

Colleges, School and Institutes

External organisations

  • Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK.
  • Sir William Dunn School of Pathology, South Parks Road, OX1 3RE Oxford, UK. Electronic address: david.greaves@hertford.ox.ac.uk.

Abstract

Phagocytosis of pathogens, apoptotic cells and debris is a key feature of macrophage function in host defense and tissue homeostasis. Quantification of macrophage phagocytosis in vitro has traditionally been technically challenging. Here we report the optimization and validation of the IncuCyte ZOOM® real time imaging platform for macrophage phagocytosis based on pHrodo® pathogen bioparticles, which only fluoresce when localized in the acidic environment of the phagolysosome. Image analysis and fluorescence quantification were performed with the automated IncuCyte™ Basic Software. Titration of the bioparticle number showed that the system is more sensitive than a spectrofluorometer, as it can detect phagocytosis when using 20× less E. coli bioparticles. We exemplified the power of this real time imaging platform by studying phagocytosis of murine alveolar, bone marrow and peritoneal macrophages. We further demonstrate the ability of this platform to study modulation of the phagocytic process, as pharmacological inhibitors of phagocytosis suppressed bioparticle uptake in a concentration-dependent manner, whereas opsonins augmented phagocytosis. We also investigated the effects of macrophage polarization on E. coli phagocytosis. Bone marrow-derived macrophage (BMDM) priming with M2 stimuli, such as IL-4 and IL-10 resulted in higher engulfment of bioparticles in comparison with M1 polarization. Moreover, we demonstrated that tolerization of BMDMs with lipopolysaccharide (LPS) results in impaired E. coli bioparticle phagocytosis. This novel real time assay will enable researchers to quantify macrophage phagocytosis with a higher degree of accuracy and sensitivity and will allow investigation of limited populations of primary phagocytes in vitro.

Details

Original languageEnglish
Pages (from-to)107-19
Number of pages13
JournalBiochemical Pharmacology
Volume116
Publication statusPublished - 15 Sep 2016

Keywords

  • Animals, Bone Marrow Cells, Cell Line, Cell-Derived Microparticles, Cells, Cultured, Endotoxins, Escherichia coli, Humans, Image Processing, Computer-Assisted, Induced Pluripotent Stem Cells, Interleukins, Macrophage Activation, Macrophages, Macrophages, Alveolar, Macrophages, Peritoneal, Mice, Mice, Inbred C57BL, Microscopy, Fluorescence, Opsonin Proteins, Phagocytosis, RAW 264.7 Cells, Staphylococcus aureus, Comparative Study, Journal Article, Validation Studies