Details of phagocytosis – the engulfing of microorganisms and debris by immune cells – revealed with specialised microscopy
With its target in reach, it opens wide and swallows it whole. This is phagocytosis; a process immune cells use to ingest harmful micro-organisms. Phagocytosis requires a cell to quickly reorganise its architecture to bend its membrane and change shape. This involves a complex of proteins called actomyosin, though the molecular details are unclear. Here, researchers combined live-cell lattice light-sheet microscopy (LLSM) and microparticle traction force microscopy (MP-TFM) to investigate the proteins involved and forces generated in real-time as immune cells ingest microparticles. During ingestion (pictured), the microparticles were squeezed — a process called constriction. The team revealed that constriction is driven by a protein complex called Arp2/3 which assembles protrusions of actin (grey), myosin 1e and 1f, taking on the appearance of a ring of teeth. As the macrophage closes in around the microparticle, myosin-II plays a role. This brings us closer to understanding how our body fights infection.
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