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Immune Response
The immune system is a combination of tissues, cells and specific mechanisms that all work
together to fight diseases and infections. With the human body being vulnerable to infections by
foreign pathogens these immune systems help avoid harm to the body. There are many ways
our body is adapted to fight pathogens from physical barriers to specialized white blood cells
therefore the immune system is categorized into two main sub sections: Specific immune
response and non-specific immune responses. (2)
- Non-Specific Immune Response
Physical Defense
One of the main ways our body is designed to involuntarily protect itself from infection and
disease is through the layer of dead cells that surrounds our entire body which is known as the
skin. The skin plays a crucial role in aiding in stopping pathogens from invading the human
body. This is done in two ways firstly the skin is thick layer that completely stops the pathogens
from penetrating in addition the skin includes of 3 layers making It even harder for pathogens to
enter. Another way the human body is adapted to fight infections and diseases through the skin
is due to the presence of immune cells such as Langerhans cells. These Langerhans cells are
mandatory for the regulation of immune cells and serve a greater purpose in protecting the
human body from harmful pathogens. (1,3)
Another important physical line of defense imbedded into our body is the presence of Cilia in
the nose. This is a defense mechanism as the cilia filters and captures particles that stop
particulates such as duct, pollen, and microbes from entering the body. The cilia also protect the
respiratory system as any harmful microbes entering through the nose may enter the lungs and
cause damage leading to infections. Therefore, proving that the presence of cilia in nose is
crucial to protect the respiratory system from microbes. After the any particles or microbes have
been captured by the cilia is then either sneezed out of the nose or is swallowed alongside
mucous to kill any microbes present. (6)
Chemical Defense
One of the most advanced mechanisms in our body that aids in chemical defense against
pathogens and other microbes is the presence of HCl (Hydrochloric Acid) in our stomach. The
HCl is part of the digestive and immune systems. This is because majority of the pathogens and
microbes ingested or inhaled usually end up in the stomach therefore this extremely acidic HCl
is used to kill bacteria that makes its way to the stomach as most bacteria's can adapt to survive
in extreme environments but not as extreme as the ph in the stomach. Therefore, concluding the
presence of HCl in the stomach and its function in helping the body be safe from foreign
pathogens or microbes. (7)
Lysosomes are another chemical defense mechanism that protects our body from infections
caused by infectious microbes. This digestive enzyme aids in the secretion of bodily fluids such
as tears and saliva. These antimicrobial agents inhibit the growth of pathogens aiding the
immune system stop the cause of infection in the human body.
, Biological Defense
When our bodies detect any wound or incision leading to pathogens entering the body, there are
two innate responses that could be stimulated to fight the growth of the foreign pathogens.
Which is either an inflammatory response or the process of phagocytosis.
The first stage in the inflammatory response includes the detection of the microbes. Microbes
that have entered the body are detected by the pattern recognition receptors that are present on
the inflammatory lipid. These receptors detect the presence of PAMPs and DAMPs. These
inflammatory mediators are release and chemicals such as leukotrienes, prostaglandins, PAF
and nitric oxide which all start to act on the smooth muscles around the infected tissue causing
vasodilation which is the widening of the arteries. Vasodilation leads to the increase in volume
of blood in the site of inflammation while decreasing the blood flow which is responsible for
the redness often associated with inflammation. This is useful as it helps contain the infection to
the site and to avoid the pathogens from flowing to other parts of the body through the blood
stream and enter the infectious tissue fluid. In addition, the increase in blood volume means that
immune cells leave the circulation can now move into the tissue fluid to try eliminating the
microbes. Nitric acid leads to vascular permeability that allows fluid to exit the blood
circulation and enter the tissue fluid leading to inflammation. (9)
Phagocytosis is another multi
step process that is innate
regardless of the type of
pathogens that have entered
the body. Initially, once any
sort of pathogens has
penetrated inside the body it
is detected by phagocytes
receptors that detected the
presence of the PAMPs which
are antigens present on their
body. This then triggers the
process of phagocytosis. The
first step of phagocytosis
includes phagocytes that start to surround the pathogen present and therefore starts to grow a
cytoplasmic extension to begin the engulfing. The pathogens are then engulfed into the
cytoplasm of the phagocytes using vesicles called phagosomes through the endocytosis process.
Then the engulfed pathogen is transported within cells through the phagosome to bind with
lysosomes present in the cell. Upon the fusion between the lysosome and phagosome the
lysosome enters is released onto the pathogen leading to the phagosome which then hydrolyses
the pathogen and organically digests it. Then proteins broken down from the hydrolysis of the
pathogen, such as protein and other nutrients, are then absorbed by the phagocytes. (11)
- Specific Immune Response
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