Question:
It looks evidant that all people similarily exposed to any disease or
disorder causing agent--substance, pathoges etc. may not get the same
disease.
How it happens? Is it due to differeance in immune strength, or due to
inherited or aquired Predispositions, sensitivity or susceptibility to
that disease?
Answer:
Immune status: The status of ones immune system also plays a major role
in how we respond to pathogens. If you've been exposed to a pathogen
before your immune system will usually remember it, and prevent further
infections by the same pathogen. Likewise, if you've recently been
infected, or under stress, your immune system will be "worn down" and
less likely to counter a new infection.
As for toxins, it's very, very complicated and varies from toxin to
toxin. All of the factors listed above can impact on our sensitivity to
toxins, plus the specifics of how the toxin works, plus other factors.
Well explained, thanks. Except Dose, Other looks to be other than
pathogenic factors. Does it not give more weightage to previously
indicated "miasma theory" than "germ theory"?
Stress is related to activating many conditions(TB, cancer). Can you
tell some physiology of stress?
The dose effect is quite simply a matter of statistical
probability. In order for an infectious agent to take hold in your body
it must:
1) gain access to your body
2) enter a region of your body conducive to the pathogens reproduction
3) avoid the immune system long enough to establish itself
A single pathogen can achieve all three of these, and thus cause an
infection. The likelihood of this occurring varies from pathogen to
pathogen, but generally speaking the likelihood of a single pathogen
leading to disease is small. But if you have two pathogens the
likelihood of infection doubles. Five pathogens are 5x more likely to
induce an infection. 1,000,000 pathogens, 1,000,000 times more likely.
One can do it, but the more pathogens you receive the more likely it
is a productive infection will occur.
Wow, there's a broad question. How stress effects the body is a huge
area of research, and one which I only know a small part of (the part
affecting immunity). Basically, in your brain is a series of centers we
call the hypothalamus-pituitary-adrenal axis (adrenals aren't in your
brain, but they're controlled by it). Basically, when you're stressed
(be it emotional, physical, illness, etc) this axis becomes activated.
This results in the production of a variety of stress hormones (cortisol
being the major one). Wiki has a pretty good into to the HPA-axis:
http://en.wikipedia.org/wiki/Hypothalamic-pituitary-adrenal_axis
Anyways, these hormones impact on a number of our bodies systems - the
digestive tract and immune system experiencing the biggest effects.
These stress hormones effect immunity at a number of levels - they
inhibit the development of immune cells in the bone marrow and thymus,
they inhibit activation of immune cells in response to pathogens, and
they alter the type of response that develops if an immune response
forms. The end effect of this is that long-term stress weakens the
immune system. Why this occurs is a total mystery - times of stress are
often times you most need your immune system.
It is one of the theories out there that try to explain why
immune cells become less active after chronic stress. But it has not
been proven; neither have any of the other theories of why stress
inhibits the immune system.
One thing that argues against this is the physiological changes which
occur during stress - there are large changes in the number and types of
proteins some immune cell carry. These changes suggest that the change
is a little more then developing tolerance to the stress hormones.
In my opinion, tolerance to stress hormones is likely a part of the
reason why this occurs, but is only one of several factors which result
in these changes.
