| | There is no doubt that the environment that we live in is "dirty". Of
course, by dirty we mean, filled with the undesirable and harmful. Each
day we fight it with antibacterial cleaners, soaps and medicines. The
more aware spend countless hours of their lives cleaning their hands
and bodies, washing away billions of antigens - bacteria, viruses,
protozoa, et ctera. They have an alertness to the thousand-year-old
battle that has been going on both within and without the body to
"arrest and cure disease," quoting Herlihy(2007).
To understand the body's defense frontlines, one must first understand
the components, processes and mechanisms that run and maintain the
human immune system. These include the mechanical and chemical
barriers, phagocytosis and killer cells, inflammation/fevers,
protective proteins and specific immunity. But time and space here does
not permit a thorough description of all of these, therefore the focus
will be on a few immunity responses - a mosquito bite, a poison ivy
reaction, and specific(acquired) immunity.
A lone mosquito finds your arm a tasty treat until your nervous system
relates to the brain that there is a cutaneous release of histamine by
your mast cells. As soon as you get that message, you look over and
slap the irritation. This histamine release is from the mast cells
being challenged - in this case by the mosquito's beak and saliva. What
actually happens, is that the proteins or polysaccharides within the
mosquito's saliva bind with the IgE antibodies, stimulating the mast
cells to release various preformed and lipid mediators. The most
notable of these chemicals is histamine. Histamine dilates venules,
activates the endothelium, and increases blood vessel permeability.
What happens next can be seen by the naked eye as swelling, redness and
warmth. Of course, the area will itch as well, since all this activity
irritates all of the nerve endings nearby, which then tell you to
"squash that bug."
Another allergy, known as contact dermititus, can be caused by plants
such as poison ivy. This immune system response varies from the
previous in that the T-cells are doing the work here. Let's say you
brush up against some of that nasty stuff out in the forest. Well, this
oil from the plant, called urushiol, rubs off onto your arm. Well,
urushiol has an odd property by which it tends to bind to and
chemically react with proteins on exposed skin cells. T lymphocytes
then begin to attack the affected cells as if those skin cells were not
part of the body. The attack is actually directed towards the complexes
of urushiol, which since have already reacted with the skin cells,
causes swelling, redness, itching, even blisters and vesicles. The good
news is, if you don't itch too much or don't have too severe of an
allergic reaction, you'll get over it in a week or two. If, perchance,
your mast cells release too many of their granules, they may cause
massive vasodilation and bronchoconstriction, a severe reaction called
anaphylaxis.
Now coming to specific immunity, the body often comes in contact with
the same pathogens at various stages in it's life. To protect itself
from a recurring illness or attack, our bodies will "remember" those
pathogens by means of a specific antibody. We use the word antibody as
a simple way to describe immunoglobulins secreted by B lymphocytes.
Theses antibodies work by attacking antigen membranes and binding with
the antigen, making it much easier for phagocytic cells(including
macrophages) to destroy the antigen. They also secrete various
complement proteins that facilitate the destruction of pathogens by
phagocytes. |
| | Posted 9/9/2008 8:52 PM - 105 Views - 8 eProps - 4 comments
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