Page 153 - The Cell in 40 Topics

he immune system that protects our bodies against enemy
bacteria and viruses works much like a disciplined army. The
immune system’s war against our microscopic enemies con-
sists of three major stages:
1- Identification of the foe: first intervention.
2- Intervention by the real army: intense warfare.
3- Return to peacetime conditions.
Before declaring war, the immune system first has to identify the foe
and obtain intelligence regarding it. Every war differs, according to the na-
ture of the enemy. And unless this intelligence-gathering is done properly,
our immune system could attack our own cells by mistake.
The first intervention comes from the phagocytes, the body’s “dust-
men” or janitors. The phagocytes declare war on the enemy. They are
rather like infantry units that establish the first contact with enemy combat-
ants (Figure 117).
Sometimes the phagocytes are unable to match the speed at which the
enemy multiplies. In that event, the macrophages go into action.
Macrophages may be compared to cavalry striking at the mass of the

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