Page 92 - The Miracle in the Immune System
P. 92

90      THE MIRACLE OF THE IMMUNE SYSTEM

              The ability of the helper T cell to produce a mole-
           cule, which activates another cell, is a very important
           process.
              First, the production of this molecule is related to
           an impending war strategy. It is obvious that the cells
           cannot make up this strategy themselves, nor can the
           strategy come about by sheer coincidence.
              Developing a strategy would not be enough either.
           The molecule in the cell, which will switch on the pro-
           duction key in the other cell, should be synthesised ac-
           curately. For this, it has to be perfectly aware of the
           chemical structure of the opposite cell.
              A mistake made in the production of this molecule
           alone would paralyze the defence system entirely. This


               How do Helper-T cells start action?

    Microscopic        Antigen complex
    pieces
                                        Helper-T (CD4) cell

                     Antigen
                                  Antigen
                     containing cell
                                  Receptor
                                      CD4



         Microbe

          The picture illustrates how a cell breaks a microbe apart and
          presents it to the T cell. As the picture at the right indicates,
          the T cell will be activated only if its antigen receptor fits to the
          presented antigen, if the CD4 molecule adheres to the antigen
          complex, and if some other molecules (right) combine with
          each other. These safety mechanisms prevent a mature T cell
          from moounting an immune attack against its host.
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