Now, you might ask in a fever condition, why on a world
would you ever want to elevate body temperature?
There are couple of theories out there why an
internal body temperature increase during
a fever maybe an advantage. The one is, higher
internal temperatures do decrease
bacterial growth. They increase lymphocyte proliferation.
Therefore, there are lymphocyte available.
They also in vow neutrophils to extra
vascularize, meaning that they go from within
the blood to albumin, or outside of the blood, so
they can maybe attack a various infection.
But interesting, even though there are two or
three mechanisms by which an elevated
temperature maybe an advantage. Studies have
shown that if you give antipyretic therapies,
such as a COX inhibitor, like Tylenol or aspirin,
usually don’t affect the outcome of someone’s
illness. And so, often times, the physician will
undergo antipyretic therapies simply because
it doesn’t really affect their outcomes and it
decreases the fever of the patient.
Now, what are the some other ways in which body
temperature does increase?
It could have be induced by something like a virus
through a number of different types of
bacteria especially Gram-negative bacteria such as
lipopolysaccharides or LPS.
And this is often times you use to experimentally to
induce fever in animals.
There are also certain fungi that will increase
body temperature or causes fever.
So, besides the microbial mechanisms to
increase body temperature, there are some
non-microbial mechanisms. One of them is: antigens,
such as if you’re rejecting a foreign particle,
inflammatory agents such as things like asbestosis
or other types of agents, that which
you’re immune system will try to attack.
There are also can be some plant particles
that cause and fever.
And finally, there are host-derived mechanisms.
So this are things that you produce yourself
such as bile acids, or urate crystals that actually
can cause an increase in body temperature
if they rise to a high enough level.
Now, what are the different seemingly molecules that
There are four primary ones that we need to
concern ourselves with:
The first is Interleukin beta, Interleukin 6,
Tumor Necrosis Factor alpha, and Interferon alpha,
are the main contributors to an increase in
temperature and use by fever.
There are host of others but the four primary
ones are the most important.
Now, how do we get this cytokine signals to the
brain to actually causes to have a fever?
There are couple of mechanisms that are likely involved.
The first is, that these substances can signal
through the blood-brain barrier, through the
endothelial cells that cause an increase in
prostaglandins, which could cause a fever.
It could go through perivascular macrophages,
also associated with the blood brain barrier,
to increase the amount of prostaglandins.
And finally, there is through a mechanism through
the astrocytes involving Rank or Rank L
that increase prostaglandin synthesis. These all are
central mechanisms. There is one
peripheral one and that is peripheral macrophages,
whether be in the lungs or
the liver can increase prostaglandin synthesis.
And these prostaglandins may be able to
directly signal the brain.
Now, how would a peripheral signal get to the brain?
This is something that is a hard to think about because
it has to make it through the blood-brain barrier.