The innate or natural immune system is that part of the
immune system that we are born with. The innate immune system keeps out
invading organisms (pathogens) such as viruses,
bacteria and fungii via a number of mechanisms.
These include
-
physical barriers such as the skin, the blood-brain-barrier
and mucous layers;
-
mechanisms such as fever to overheat the invaders.
-
pathogen destroying enzymes secreted in mucous layers and
elsewhere;
-
the complement - a system of plasma proteins
that principally attack bacteria;
-
the inflammatory response which involves the action of several
biochemicals including histamines, kinins,
cytokines,
chemokines,
neutrophils
and mast cells among others, which destroy
pathogens, ready cells to resist attack and regulate other parts of the
immune response.
-
non-specific white blood cells called effector
cells, principally the macrophages which
gobble up pathogens;
All these immune mechanisms are unable to recognise specific
invaders which contrasts with the acquired
immune system that "learns" to recognise invading pathogens by exposure
to them.
Innate immunity is always present in the body and can
react very quickly to an infection. The fact that it is non-specific allows
it to target most invaders without previously having come across them.
The division between the innate and acquired immune systems
is far from complete and there are several interactions and feedback mechanisms
in operation between the two. These include cytokine
secretion, antigen presentation
and cell-to-cell communication.
Innate Immunity Links:
Innate
(non-specific) Immunity
Non
Specific "Innate" Immunity
Innate
Human Immunity
Interrelationship
between innate & acquired immunity
Innate
versus adaptive immunity
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