Page 95 - The Miracle in the Immune System
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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-
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