Page 98 - The Miracle in the Immune System
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96 THE MIRACLE OF THE IMMUNE SYSTEM
Peptide fragment
of antigen
Peptide-presenting site
Antigen-presenting cell
(macrophage)
Examples of APCs are macrophages. They do this by taking
the foreign material into a cavity in their cytoplasm - the part
of the cell outside the nucleus - and adding digestive chem-
icals to them. These chemicals break the bacteria into frag-
ments of the proteins from which they are made, fragments
that are now harmless, but which can also be utilised.
the human body, identify the enemy and present the en-
emy it captures to the T cells for them to provide intel-
ligence about it.
Why would the cell do this? According to the theo-
ry of evolution, this cell should be concerned only
about its own well-being. However, it serves the sys-
tem, although it receives no benefit from it.
What is even more interesting is that the APC are
very well aware of the requirements of the T cells.
Based on this, the APC will break down the enemy cell
