Page 66 - The Miracle in the Immune System
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64 THE MIRACLE OF THE IMMUNE SYSTEM
Phagocytosis in progress. The macrophage (yellow) while
digesting the bacteria (blue).
Phagocytes, considered the "police forces of the
body," can be examined under two separate headings.
1. Mobile police forces: These roam in the blood
and shuttle forwards and backwards between the tis-
sues when required. These cell units, which circulate
throughout the body, also serve as scavengers.
2. Immobile police forces: These are immobile ma-
crophages, which are situated in the gaps in various tis-
sues. They perform phagocytosis on the
micro-organisms from where they are, without moving.
If the invader antigens (foreign micro-organisms)
are few enough for the present eater cells to deal with,
they are destroyed with no extra alarm being given. But
if the invader microbes are too great in number, the
eater cells may fail to get them under control. Unable to
