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Macrophage phagocytosis

Published on January 30, 2013   34 min

A selection of talks on Biochemistry

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This talk describing macrophage phagocytosis is presented by Joel Swanson from the Department of Microbiology and Immunology at the University of Michigan Medical School.
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Phagocytosis is the process by which cells ingest other cells or particles, was a defining feature of macrophages when they were first described in the 19th century. Macrophages are capable of ingesting large quantities of extracellular debris, particles, or microbes. Their ability to do so is essential to their roles in innate and adaptive immunity. The image shown here is a scanning electron micrograph of a mouse bone marrow-derived macrophage caught in the act of ingesting sheep red blood cells by phagocytosis. The macrophage, which has been pseudocolored blue, is spread onto a glass surface. The sheep red blood cells had been coated with immunoglobulin G, or IgG, to opsonize or prepare them for the process of phagocytosis. In this image, the red cells, pseudocolored red, are visible in various stages of engulfment by extensions of macrophage plasma membrane.
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This image shows the same macrophage viewed by phase-contrast light microscopy. Surface protrusions called ruffles appear as dark, wavy lines at the margins of the cell. The red line indicates the profile of a macrophage spread flat onto the glass cover slip. This is the first frame of a time lapse video recording which shows actual movements accelerated 100-fold. The video shows the active movements of the surface ruffles and erythrocytes falling out of the buffer and onto the macrophage. After binding to the cell, the red blood cells change from bright to dark as phagocytic cups from the macrophage surface extend out over the particle. This is particularly evident in the lower part of the image, where several erythrocytes are internalized in rapid succession. Once internalized, the red cells remain dark by phase-contrast optics and move towards the center of the cell. Although many kinds of cells are capable of phagocytosis,