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
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 and lymphocytes.
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
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 is necessary.
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, in this book, these extraordinary events
are told in an easy-to-understand way.