Step By Step To All-Out War
Until now, we have discussed the
general structure of the defence system, its organs,
cells, and enemies. In this chapter, we will explore
the deadly warfare between our defence system and
enemy cells, and the wonderful defence our body mounts.
The brave battle fought by of our
defence system is comprised of three important stages:
of the enemy, first action.
2. The attack of
the real army, all-out war.
3. Retreat to a
The defence system has to clearly
identify the enemy before it starts the fight. This
is because each engagement differs from the other
depending on the type of enemy. Moreover, if this
piece of intelligence is not properly handed on, our
defence system may inadvertently attack the body's
The phagocytes, known as the scavenger
cells of the defence system, take the first action.
They fight hand-to-hand with the enemy. They are just
like infantrymen who fight with bayonets against enemy
Sometimes, phagocytes cannot catch
up with the increasing numbers of the enemy, at which
point big phagocytic cells, macrophages cut in. We
can liken the macrophage to cavalrymen cleaving their
way through the middle of the foe. At the same time,
macrophages secrete a fluid, which sets off a general
alarm in the body to increase the body temperature.
Macrophages have yet another important
characteristic. When a macrophage cell captures and
engulfs a virus, it tears off a special portion of
the virus, which it carries on itself like a flag.
This serves as a sign for the other elements of the
defence system as well as an item of information.
Once the gathered intelligence is
forwarded to the helper T cells, by the help of which
they identify the enemy, their first task is to immediately
alert the killer T cells, stimulating them to multiply.
Within a short period, the stimulated killer T cells
will become a formidable army. This is not the only
function of the helper T cells. They also ensure that
more phagocytes arrive at the battlefront while they
transfer the gathered intelligence relating to the
enemy to the spleen and lymph nodes.
Once the lymph nodes receive this
information, the B cells, which have been waiting
for their turn, are activated. (The B cells are manufactured
in the bone marrow and then migrate to the lymph nodes
to wait for their turn to be of service).
THE WAR BEGINS
As viruses start to
invade the body, some will be captured by the
antigens with the assistance of the macrophages
and subsequently destroyed. Some of millions
of T helper cells travelling in the circulatory
system have the ability to "read" this specific
antigen. These particular T cells become active
when they bind to the macrophages.
helper T cells begin to multiply. They then
warn the killer T cells and B cells, which are
few in number and sensitive to the enemy virus,
to multiply. When the number of B cells increases,
the helper T cells send them a type of signal
to initiate the manufacturing of antibodies.
DEFEATING THE INFECTION
At this point,
some viruses have successfully penetrated the
cells. The only place where viruses can multiply
is in the body cells. With the chemical materials
they secrete, killer T cells cause the death
of these cells by drilling through their membranes,
and removing the elements inside. Thus they
prevent the virus in the cell from reproducing.
By holding directly on to the surface of the
virus, antibodies inactivate them and prevent
them from invading other cells. In conclusion,
cells that are infected are destroyed with the
aid of chemical substances, which were prepared
prior to the attack.
4. AFTER THE WAR
the battle is won, and the disease has been
eradicated, suppressor T cells stop the whole
offensive system. Memory T and B cells remain
in the blood and lymphatic system in order to
become immediately activated in case a virus
of the same type is met.
The activated B cells go through
a number of stages. Every stimulated B cell begins
to multiply. The multiplication process continues
until thousands of identical cells are formed. Then,
the B cells, which are ready for war, start to divide
and are transformed into plasma cells. Plasma cells
also secrete antibodies, which will be used as weapons
during the fight with the enemy. As stated in earlier
chapters, B cells are capable of producing thousands
of antibodies in a second. These weapons are very
handy. They are capable enough to bind to the enemy
first, and then to destroy the biological structure
of the enemy (antigen).
If the virus penetrates the cell,
the antibodies cannot capture the virus. At this point,
the killer T cells come into play again and, by identifying
the viruses in the cell with the help of MHC molecules,
they kill the cell.
However, if the virus has been successfully
camouflaged, escaping even the notice of killer T
cells, then "natural killer cells", briefly called
NKs, swing into action. These cells destroy the cells
which host viruses in them, and which are imperceptible
to other cells.
After the victory is won, suppressor T cells stop
the war. Although the war is over, it is never to
be forgotten. Memory cells have stored the enemy in
their memory. Staying in the body for years, these
cells help the defence to be faster and more effective
if the same enemy is encountered again.
The heroes of this war have not received
any military training. The heroes of this war are
not human beings able to reason.
The heroes of this war are cells
so minuscule as to hardly cover a full stop when they
come together in millions.
Moreover, this amazing army does not engage in fighting
alone. It manufactures all the weapons it will use
during the war; it makes all war plans and strategies
itself, and cleans up the battleground after the war.
If all these processes were left in the control of
man, and not cells, would we ever be able to handle
such a feat of organization?