Three Parts of the Immune System

All living organisms, especially animals, have to protect themselves from external,
harmful viruses and germs. Moreover, unhealthy body cells need resistance for there is
the possibility of them becoming infectious. In the process of development there are three
different layers of defense.

The first layer of defense is the skin, membranes, and different kinds of secretions.

The second layer of defense are the white blood cells, the
proteins that defend small cell organisms and respond to inflammation. These are two
unspecific defenses because they defend without differentiating the germs. The second
layer of defense is activated by chemical signals; phagocytes and proteins that defend
small cell organisms both attack the germs that have survived the first layer of defense.
Increased inflammation in the body is a sign of the engagement of the second layered
defense.

The third layer of defense is an innate defense of the immune system. The immune
system is a network of cell tissues and organs that work together to defend the body against attacks by foreign invaders. These are primarily microbes (germs)-tiny, infection-
causing organisms such as bacteria, viruses, parasites and fungi. This defense is a specific defense because it produce different kinds of antidotes depending upon various cause of
infections. The immune system is amazingly complex. It can recognize and remember
millions of different enemies, and it can produce secretions and cells to match up with
and wipe out each one of them.