Page 95 - The Miracle in the Immune System

Cells On Duty In The System 93

ready for use. Scientists were amazed to discover the
fact that the cell produces its own weapon by itself and
stores it for future use. Even more amazing are the de-
tails in the mind-boggling way the cell uses this chemical
weapon.
When an enemy approaches the host cell, these mi-
crogranules move to the tip of the cell in the direction
of the enemy. Afterwards, they come in contact with
the cell membrane, melt into it, and by extending to-
wards the outside, they release the substance contained
within them.

Natural Killer Cells: "NK"
These lymphocytes, which are produced in the
bone marrow, are also available in the spleen, lymph
node, and the thymus. Their most important functions
are killing tumour cells and virus-carrier cells.
From time to time, invader cells take very sinister
courses. They sometimes hide so well in body cells that
neither antibodies nor T cells recognise the enemy. Ev-
erything seems usual from the outside. In such cases,
the defence system somehow suspects an anomaly and
"NK" cells rush to that region through the blood. Killer
lymphocytes surround the cell and start to push the cell
around. At that stage, the enemy cell is killed by a toxi-
genic substance injected inside it.
How these cells identify the enemy is yet another
unanswered question about the defence system. The
receptors that should be present on their surfaces to
enable them to identify of the target cells have not yet
been discovered. Therefore, the mechanism they em-