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Your immune system is your body's main defense system and is made of
many parts such as your skin, bone marrow and spleen - but these are just
some of the immune system parts so we will look at the different parts of
the immune system and how they work to protect your body. The first
is the the skin, it is your body's first defense as it acts as an outer
barrier to viruses and disease. Your skin protects your body much
the same way as you would use plastic wrap to protect food. There
are other entrances to the body - your nose, mouth and eyes are all entry
points for germs and viruses.
The nasal passage and lung is coated with mucus which traps many germs
that may not be killed. Lysozyme is an enzyme found in tears and
mucus. This enzyme breaks down the cell walls of many bacteria.
Any bacteria or virus entering the body must first past these defenses.
Once inside, the immune system acts at a different level using different
components of the immune system - Lymph system - Thymus - Spleen - Bone
Marrow - White blood cells - Antibodies - Complement system - Hormones.
Let us examine each of these components in detail:-
Lymph System
This is where a clear liquid bathes the cells with water and nutrients.
The liquid is pushed by body and muscle motion to the lymph nodes.
The Lymph nodes contain filtering tissue and a large number of lymph
cells. When fighting certain bacterial infections, the lymph nodes
swell with bacteria and the cells fighting the bacteria, to the point
where you can actually fell them. Swollen lymph nodes are therefore
a good indication that you have an infection of some sort.
Thymus
Thymus is responsible for producing mature T cells (white blood cells).
An adult can live without the thymus because other parts of the immune
system can handle the load but with newborn babies the immune system
collapses and baby dies. Bone Marrow
The bone marrow is your body's blood cell factory. Red blood cells
are produced in the marrow and enter the bloodstream fully formed.
White blood cells are produced in the marrow but some of these cells
travel to the Thymus to mature. We will go into white blood cells in
greater detail later on. All blood cells are produced from stem
cells. Stem cells change into actual, specific types of white blood
cells. Antibodies
These are immunoglobulins and gammaglobulins which are produced by white
blood cells. They are proteins that respond to specific antigen
(bacteria, virus or toxins). When an antibody binds to a toxin it is
called an antitoxin. The binding disables the chemical action of the
toxin. Antibodies bind to the outer coat of the virus or the cell
wall of the bacteria stopping the movement of the virus or bacteria.
Large numbers of antibodies bind to an invader and signal to the
complement system that the invader needs to be removed. Antibodies
come in five classes: Immunoglobulin A; D; E; G and M. Spleen
The spleen works as a blood filter. It filters the blood from
foreign cells and old red cells in need of replacement.
The Complement
System
The complement system are proteins much like antibodies and are
manufactured in the liver. These proteins are activated by and work
with the antibodies, hence the name. They cause a bursting of the
cells and signal to phagocytes that a cell needs to be removed.
Hormones
Hormones can directly affect the immune system - corticosteroid (a
component of adrenaline) can suppress the immune system while tymosin is a
hormone that causes lymphocytes (T and B cells - white blood cell)
production. Interleukins are another type of hormone produced by
macrophage (white blood cell) after eating a foreign cell. Other
hormones like IL-1 produces fever and fatigue upon reaching the
hypothalamus. The raised temperature of a fever can kill some
bacteria. Tumor Necrosis Factor are able to kill tumor cells and promote
the creation of new blood vessels. They are produced by macrophages.
Interferons are proteins (like antibodies and complements) which allow
cells to signal to one another. When an interferons binds to a cell
it produces proteins that help prevent viral replication in the cell.
White Blood Cells are probably the most important part of the immune
system and are a number of different cells working together to fight and
kill bacteria, virus and infections. The White Blood Cells are:-
Leukocytes; Lymphocyte; Monocytes; Granulocytes; B-cells; Plasma cells;
T-cells; Helper T-cells; Kill T-cells; Suppressor T-cells; Natural killer
cells; Neutrophils; Eosinophils; Basophils; Phagocytes; Macrophages.
Leukocytes are divided into three classes Granulocytes; Lymphocytes;
Monocytes.
Granulocytes contain different chemicals depending on there type.
They are divided into three classes: Neutrophils, Eosinophils and
Basophils.
Neutrophils are the most common white blood cell found in your body.
The bone marrow produces trillions everyday and they are released into the
bloodstream; their life span is generally less than a day.
Neutrophils are attracted to foreign material, inflammation and bacteria.
Once a neutrophil finds a foreign particle or a bacteria it will engulf
it, releasing enzymes, hydrogen peroxide and other chemicals from its
granules to kill the bacteria.
Eosinophils focus on parasites in the skin and the lungs.
Basophils carry histamine therefore causing inflammation. This
causes more blood and dilates capillary walls so that more immune system
cells can get to the infected site.
Lymphocytes come in two classes: B cells (those that mature in bone
marrow) and T cells (those that mature in the thymus).
B cells produce antibodies. When a germ is present in the body the B
cell clones itself and produces millions of antibodies designed to
eliminate the germ.
T cells known as Killer T cells can detect cells in your body that are
harboring viruses, and when it detects such a cell it kills it. Two
other types of T cells, known as Helper and Suppressor T cells, help
sensitize T cells and control the immune response.
Monocytes mature into macrophages.
Most boundary tissue has its own devoted macrophages. For example,
alveolar macrophages live in the lungs and keep the lungs clean (by
ingesting foreign particles like smoke and dust) and disease free (by
ingesting bacteria and microbes). Macrophages are called langerhans
cells when they live in the skin. Macrophages also swim freely.
One of their jobs is to clean up dead neutrophils - as part of the healing
process. VIRUS & BACTERIA A virus particle is nothing but a fragment
of DNA in a protective coat. The virus comes in contact with a cell,
attaches itself to the cell wall and injects its DNA into the cell.
The DNA uses the machinery inside the living cell to reproduce new virus
particles. Eventually the hijacked cell dies and bursts, freeing the
new virus particles; or the viral particles may bud off from the
cell so it remains alive. In either case, the cell is a factory for
the virus.
Bacteria are completely independent organisms able to eat and reproduce -
they are sort of like fish swimming in the ocean of your body. Under
the right conditions bacteria reproduce very quickly: One bacteria
divides into two separate bacteria perhaps once every 20 or 30 minutes.
At that rate, one bacteria can become millions in just a few hours.
VACCINATIONS B cells can recognize a virus and produce antibodies for
it. However, there are only a few of these cells for each antibody.
Once a particular disease is recognized by these few specific B cells, the
B cells turn into plasma cells, clone themselves and start pumping out
antibodies. This process takes time, but the disease runs it course
and is eventually eliminated. However, while it is being eliminated,
other B cells for the disease clone themselves but do not generate
antibodies. This second set of B cells remains in your body for
years, so if the disease reappears your body is able to eliminate it
immediately before it can do anything to you. This sis what happens
in the case of vaccination. A vaccine is a weakened form of a
disease. It is either a killed form of the disease, or it is a
similar but less virulent strain. Once inside your body your immune
system mounts its defense (B cell recognizing the virus), but because the
disease is weaker you get few or no symptoms of the disease. Now,
when the real disease invades your body, your body is able to eliminate it
immediately.
Vaccines exist for all sorts of diseases, both viral and bacterial;
measles, mumps, whooping cough, tuberculosis, smallpox, polio, typhoid,
etc. |
