SKM 2023 – scientific programme

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BP: Fachverband Biologische Physik

BP 28: Poster Session II

BP 28.54: Poster

Thursday, March 30, 2023, 18:00–20:00, P2/EG

The energy cost of membrane-cortex deformation in phagocytosis of different sized pathogens — •Mehdi Ait Yahia and Rhoda Joy Hawkins — University of Sheffield

During their lifetime macrophages (a type of white blood cell) defend against infection in biological organisms by moving and interacting with micrometer sized pathogens. Interactions include phagocytosis which is the engulfment of pathogens by the cell deforming around the target. We model the physical description of the deformation of the membrane and cortex composition based on the energy of bending and stretching. For the bending energy we use the Helfrich energy for an elastic membrane in terms of its elastic moduli and curvature. The stretching energy is a function of the moduli and the extra surface needed to engulf the target object. We consider different methods to obtain the elastic moduli including the possibility of exocytosis modifying the surface area. The bending energy is expected to be smaller for larger objects since the curvature is inversely proportional to the radius. On the contrary the stretching energy is expected to increase for a larger object. We minimize the sum of these two energies with respect to the radius to find an optimum size for phagocytosis. We compare our theoretical predictions with data from simulations and experiments on macrophages engulfing beads of different sizes and the fungal pathogen Cryptococcus.