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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,
