Download Macrophage Function

Macrophage
Function
A macrophage is a large white blood cell that is an important part of our immune
system. The word 'macrophage' literally means 'big eater.' Its job is to clean our
body of microscopic debris and invaders. A macrophage has the ability to locate
and 'eat' particles such as bacteria, viruses, fungi, and parasites.
The macrophage accomplishes its ongoing cleanup task by engulfing unwanted
particles and 'eating' them. A macrophage uses a process called phagocytosis to
destroy and get rid of unwanted particles in the body. Phagocytosis literally means
'eat cell.' The process works like this: as the macrophage engulfs the particle, a
pocket called a phagosome is formed around it. Then, enzymes are released into
the phagosome by an organelle within the macrophage called a lysosome. Much like
the enzymes in our own stomach are released to digest our food, the enzymes
released by the lysosome digest and break up the particle. The remaining debris, or
what is left of the particle, exits the macrophage to be absorbed back into the
body.
Another fascinating aspect of a macrophage is its ability to know which cells to
destroy and which ones to leave alone. Healthy, living cells within our body have a
particular set of proteins on their outer membrane. They are essentially ID tags
for our cells. If the cell is displaying an incorrect ID tag, the white blood cell
destroys it. This is how our immune system recognizes our own cells versus foreign
bodies.
Although macrophages do not distinguish between the different types of bacteria,
viruses, or other outsiders, they do recognize that those particles do not belong in
the body by detecting the different outer proteins. Macrophages even have the
ability to detect signals sent out by bacteria (like sharks and the smell of blood),
allowing them to travel to the site of infection. Then, once they have engulfed the
invader and started to digest it, they are able to take a part of the invader called
an ‘antigen’ and present it on the outside of their cell membrane. They present the
antigen using special proteins in their cell membrane. When it meets up with
another immune cell it announces which pathogen it is (bacteria, virus, etc.). This
helps the other cells in your immune system launch an immune response.
Structure
Macrophages are relative large white blood cells, so they have a large surface area
of membrane. The membrane is formed into many pseudopods – extensions of cell
that can grab and surround smaller cells. While they are large, they are also
flexible and can move through tissues and organs easily. Macrophages contain a
large number of lysosomes. Their cell membrane includes many special proteins for
receiving chemical messages and presenting antigens.
Structure-Function Connection:
1. Why do you think it would be beneficial for macrophages to be large and
have a large surface area of membrane with psuedopods?
2. Why might it be beneficial for macrophages to contain a lot of lysosomes?
3. Why do you think macrophages have special proteins on the outside of their
cell membranes?