Before delving into the astounding
details of the war of defence fought in the innermost
recesses of our bodies, we must first have a general
look at the defence system and its elements. Briefly,
the defence system may be defined as "an extremely disciplined,
hard-working and organized army that protects the body
from the clutches of external enemies." In this multi-faceted
war, the main duty of the elements fighting in the front
line is to prevent the enemy cells, such as bacteria
or viruses, from entering the body.
Although it is not easy for the
enemy organisms to enter the body, they exert themselves
to the utmost to reach their ultimate goal of invading
the body. When they successfully do so, after overcoming
various obstacles such as the skin, and the respiratory
and digestive tracts, they will find tough warriors
waiting for them. These tough warriors are produced
and trained in specialized centres such as the bone
marrow, spleen, thymus, and lymph nodes. These warriors
are "the defence cells" referred to as the macrophages
First, various types of phagocytes,
which are called the "the eater cells" will swing into
action. Then the macrophages, another specific type
of phagocytes, take their turn. They all destroy the
enemy by engulfing it. Macrophages also perform other
duties such as summoning other defence cells to the
battleground, and raising the body temperature. The
rise in temperature at the onset of a sickness is very
important, for the afflicted the person will feel fatigued
by it and need to rest, thus reserving the energy needed
to fight against the enemies.
If these elements of the immune
system prove insufficient against the enemies penetrating
the body, then lymphocytes, the champions of the system,
come into play. Lymphocytes are of two types; B cells
and T cells. These are again further divided into sub
The helper T cells are next in
reaching the battleground after the macrophages. They
may be considered the administrative agents of the system.
After the helper T cells identify the enemy, they warn
other cells in order to initiate a war against it.
Thus alerted, the killer T cells
come into play to destroy the besieged enemy.
The B cells are the armaments
factory of the human body. Following their stimulation
by the helper T cells, they immediately start to produce
a sort of weapon called the "antibody".
After the alarm is over, suppressor
T cells stop the activity of all defence cells, and
therefore prevent the war from lasting any longer than
However, the mission of the defence
army has not yet ended. The warrior cells, called the
memory cells, store necessary information about the
enemy in their memories and keep it for years. This
will enable the immune system to mount a quick defence
against the same enemy at later meetings with it.
There are many more incredible
factors hidden in the details of the defence system,
which we have very briefly outlined above. As mentioned
before, on this site, these extraordinary events are
told in an easy-to-understand way.