Page 80 - The Miracle of the Immune System
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THE MIRACLE OF THE IMMUNE SYSTEM
Types of T cells
T cells come in three groups: helper T cells, killer T cells, and sup-
pressor T cells. Every T cell has a special MHC molecule enabling it to
recognize the enemy.
Helper T cells
These cells can be regarded as the administrators of the system. In
the initial stages of war, they decipher the properties of the foreigner cells
absorbed by the macrophages and other antigen catcher cells. After they
receive the due signal, they stimulate killer T and B cells to fight. This
stimulation causes B cells to produce weapons called antibodies.
How do Helper-T cells start action?
Microscopic
Antigen complex
pieces
Helper-T (CD4) cell
Antigen containing
cell Antigen
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 re-
ceptor fits to the presented antigen, if the CD4 molecule adheres to the antigen com-
plex, 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.
