Added by Paul S.
on 2012-10-30
Humans come into contact with external
agents on a daily basis, agents that could be harmful if allowed the
opportunity to enter the body. The most severe are dangerous
disease-causing microorganisms,
pathogens, or abnormal cells that arise within the body.
If bacteria or viruses do gain entry, the body is furnished with a
composite, multifaceted internal defense system — the Immune system —
that provides around the clock protection against invasion by foreign
agents.
Although it is not directly a part of the Immune system, the
skin
is the first line of defense of the body against foreign agents. Body
surfaces exposed to the external environment include the skin and
mucous membranes,
i.e., the lining of the respiratory and gastrointestinal tracts, which
are tubes, that pass through the body and are considered external to the
body.
The immune system is also involved in protection against cancerous cells and prepares the body for repair of damaged tissues.

Antibodies Attacking a Virus
The Immune system
When we talk about
Immunity, we are referring to the
body’s ability to resist or get rid of potentially dangerous foreign
materials or abnormal cells. As stated earlier, the first line of
defense of the body is attributable to the
epithelial tissues
of the body that cover the outer surface of the body (the skin) and
those that line the body cavities (such as the GI tract and respiratory
tract) that come into contact with the external environment (external
defenses). We will speak more about that in a later article.The immune
system is a system that works internally first by recognizing cells or
other agents as either ‘self’ or ‘non-self’; this is the first job of
the immune system. Once it recognizes a cell/agent as non-self it will
go on to either destroy it or neutralize it. These agents that are
non-self are generally foreign agents that have entered the body or
abnormal cells somewhere in the body that it is not supposed to be or
have mutated.The immune system responsibilities can be grouped into four
distinguishable functions:
- Guarding against pathogens (disease-causing agents such as bacteria and viruses among others);
- Removing damaged cells and tissue affected by trauma or disease clearing the way for healing and tissue repair;
- Identifying and destroying cells that have mutated or become abnormal, which are originally from the body;
- Keeping immune responses, which are inappropriate, in check that lead to allergies or autoimmune diseases.
Types of Immunity
Immune responses may either be
innate and nonspecific or
adaptive and specific. Our immune systems protect us based on the harmonizing actions of two separate but symbiotic constituents: the
Innate immune system and the
adaptive or
acquired, immune system. These two systems respond differently when it comes to timing and the selectivity of the defense mechanisms.
Innate Immunity comprises all of the body’s non-specific immune
responses. This mechanism is the body’s first response that comes into
play immediately on exposure to a threatening agent. These responses are
non-specific and inherent, meaning that they are built-in or innate,
defense mechanisms that with no preference defend against any and all
foreign or abnormal material, even on exposure to it for the first time.
Such a response allows for a first line of internal defense against a
wide array of threats, such as, infectious agents, chemical irritants,
and tissue injury from trauma and burns. We are all born with generally
the same innate-immune response mechanisms with a few slight differences
in genetic makeup.
Contrarily, adaptive or acquired immunity relies on specific immune
responses. Here, foreign materials to which the body has already been
exposed to are being selectively targeted. At this point the body has
already had an opportunity to prepare for such an attack and aim all its
resources directly at the desired foe.
The adaptive immune response hence takes a considerably longer time
to mount its attack when to compared to that of the innate system. The
innate and adaptive immune systems work in complement to each other in
order to identify, contain, then eliminate or neutralize harmful agents.
In the next article we will further explore the roles and stakeholders of these immune systems in greater detail.
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