Page 83 - The Miracle of the Immune System

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Cells on Duty in the System

of the innate system (MHC molecules) granted to them. When they locate
the invaded cell, they secrete a chemical substance. This secretion sinks
into the membrane of the cell forming a hole by lining up sideways in
close formation. Following this, leaking starts in the cell which is full of
pores, and the cell dies.
Killer T cells store this chemical weapon in granular form. This way,
this chemical weapon is always kept ready for use. Scientists were

amazed to discover the fact that the cell produces its own weapon by it-
self and stores it for future use. Even more amazing are the details in the
mind-boggling way the cell uses this chemical weapon.
When an enemy approaches the host cell, these microgranules 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 towards
the outside, they release the substance contained within them.

Natural Killer Cells: "NK"
These lymphocytes, which are produced in the bone marrow, are al-
so available in the spleen, lymph node, and the thymus. Their most im-

portant 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
recognize the enemy. Everything 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 toxigenic substance injected inside it.
How these cells identify the enemy is yet another unanswered ques-
tion 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 employ in identifying
the enemy has not yet been clearly understood.