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Course: Health and medicine > Unit 8
Lesson 11: Multiple sclerosisMultiple sclerosis risk factors
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Want to join the conversation?
- What institutions are the leaders in doing research regarding the causes of MS?(4 votes)
- What about the Southern Hemisphere? Do people living south of the equator also have higher chances of developing MS?(2 votes)
- Southern hemisphere countries include Australia, New Zealand, south America, Africa; these countries definitely lies in the hotter climate region hence less chance of developing MS however Antarctica do lie in southern part ergo opposite effect.
Simply, more sunlight less MS, less sunlight more MS.(1 vote)
- Could people in northern areas take a vitamin D supplement to help protect them against MS?(2 votes)
- This won
t be helpful at all if they don
t sunbathe. Vitamin D is only activated with exposure to the sunlight.(1 vote)
- If Identical twins have the "same" DNA and one has MS wouldn't the likely hood of the other twin having MS be higher than 30%? How is it not? Also Identical can't have the same exact DNA or they'd be the same person, so why did Jaffer say that instead of similar DNA? Is that the reasoning that one twin can get it and the other may not?(1 vote)
- The disease has both genetic and environmental factors. Identical twins will experience different environmental factors, thus the difference in occurrences.
Identical twins have nearly the exact same DNA as they develop from the same initial zygote. Any differences in DNA are from mutations occurring in growth after the zygote splits into multiple embryos.(3 votes)
- At3:56, how does vitamin D involve in regulating immune system?(0 votes)
Video transcript
- [Voiceover] So as of now,
we haven't really been able to identify one true cause
of Multiple Sclerosis. But we have been able to identify a number of both genetic and environmental factors that may be involved in
propagating the disease. So first I kinda wanna talk a
little bit about the genetics. So how do we know that there is a genetic component to the disease? Well, we do, what are
called, twin studies. So in these twin studies, what we'll do, is we'll take a pair of identical twins, and a pair of fraternal twins, and we'll compare them. So we know that identical
twins have the same DNA, and fraternal twins have different DNA. So what we can do, is we can compare the
incidence of Multiple Sclerosis in identical twins and in fraternal twins. So let's say one of the identical twins has Multiple Sclerosis, then the likelihood of the
other twin having the disease is about 25 to 30 percent. But in fraternal twins, that number is about as
low as five to 10 percent. So given the fact that identical
twins have the same DNA, and that fraternal twins
have different DNA, this tells us that there is a pretty high genetic component in Multiple Sclerosis. But Multiple Sclerosis, as
far as genetics is concerned, is actually pretty complicated. It's thought that about
over 50 genes are involved. And they're still finding
more and more to this day. Now there's actually one gene
that I want to talk about, and the reason why is because this gene is involved in autoimmunity, and it's found on Chromosome six. So, here's the chromosome in question, and you'll notice that I've actually highlighted the part here in red. And this part will contain
a gene called HLA-DRB1. And you know, this is kind
of a lot of letters here, so we'll mostly just focus on this part over here, the HLA part. So what is HLA? Well, it just stands for
Human Leukocyte Antigen. So, H-L-A. So, what does this guy do? Well, let's say that you have
any general cell over here, on this cell, you're going to
have a protein on the surface. And that is going to be our
human leukocyte antigen. This human leukocyte
antigen will then have some other kind of protein
or peptide bounded to it. And that protein or peptide may belong to something like a virus, or bacteria, or something that shouldn't belong. And so what it's gonna do, is it's actually going to
present that to another cell, namely, your T cells. So maybe we have a T cell over here. So the T cell is going
to look at this peptide that's being presented
by the original cell, and it's going to say, "Okay,
so this doesn't belong here, "so we need to kind of begin
an attack and defend the body." So really, this entire
gene is important for allowing the immune system to determine what is part of the body and what isn't part of the body. And it's thought that a
malfunction in this gene is implicated in autoimmunity. Now, remember that Multiple Sclerosis is also an autoimmune disease. So, it's thought that when
this gene malfunctions, then this could potentially
lead to Multiple Sclerosis. So that's some evidence that, you know, genetics may be involved. But now I wanna talk a little bit more about the environment. And there are a lot of different factors. So first what we're going to do is we're actually gonna look at
a picture of the earth here. So here, we have the equator. And at the equator is a pretty low incidence
of Multiple Sclerosis. And as you move north from the equator, that incidence increases. So why is that, why is there this kind of geographic spread of the disease? Well, at the equator,
there's a lot of sunlight. So people who live here will be exposed to a lot of sunlight. When you're exposed to a lot of sunlight, then your skin can actually start to produce vitamin D. So, on average, people
who live near the equator will have more vitamin
D than people who live further away from the equator. Now why is this important? Well, vitamin D is actually thought to be involved in regulating
the immune system. So a lot of immune cells, let's say you have a T cell over here, a lot of these immune cells may have a receptor for vitamin D as well. So maybe you have vitamin D here in red, and it's kind of bound to this receptor of this T cell. And when you have a
deficiency in vitamin D, it's thought that this
can lead to autoimmunity. So as you move further
and further up north, you're exposed to less sunlight. If you're exposed to less sunlight, then you have, you most likely have less vitamin D in you. If you have less vitamin D in you, then this could lead to
an autoimmune disorder, namely Multiple Sclerosis. So it's thought that
this may be the reason why the incidence of MS increases as you move away from the equator. Another environmental factor is exposure to some kind of virus in your childhood. So what kind of virus are
we talking about here? Well, there are a lot of different viruses that may be implicated. So for example, the Epstein-Barr virus, measles, mumps, and even herpes. So it's really important to know that these viruses
themselves do not directly cause Multiple Sclerosis. But if you have had exposure
to these viruses in the past, then your chances of developing the disease is increased. So why does this happen? Well, it's thought that the proteins in this virus actually
resemble some of the proteins that are found in your nervous system. And so this phenomenon is
called molecular mimicry. It's when the virus kind of resembles what's in the body, and the immune system actually kind of confuses the two. So the last thing I want
to talk about is smoking. Now we all know that smoking
is bad for your lungs, but it's also thought
that smoking may increase your chances of getting
Multiple Sclerosis. So if you look at a
group of people who smoke and who have Multiple Sclerosis, if they stop smoking, then the progression of their disease slows down. So why exactly this happens,
we're not 100 percent sure. All we know is that
there's this correlation between smoking and the
development of Multiple Sclerosis. So I've shown you a lot
of different risk factors that may be involved in
developing Multiple Sclerosis. So here on the genetic
side, you have over 50 genes that may be involved,
and I've also shown you all these different
environmental factors that may be involved as well. But unfortunately, we
haven't really been able to connect all these factors together. And because of that, we
haven't really been able to identify a single cause for the disease. But as it is right now,
these are some of the major risk factors implicated
in getting Multiple Sclerosis.