Human Physiology – Naturally and Artificially Acquired Immunity
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Human Physiology – Naturally and Artificially Acquired Immunity

>>Dr. Ketchum: So in this part we’re going
to focus on immune responses in health and disease. So to begin with, we want to look at naturally
versus artificially acquired immunity. So when you think about natural immunity, think
about the fact that you’ve somehow been exposed naturally to an antigen. If it’s
artificial immunity, then you’ve been injected with something and that injection has caused
you to mount an immune response. Okay, now regardless of whether it’s natural
or artificially acquired immunity, you have two different forms. There’s passive and
active. So what we’re going to do is go through each of these first. So we’ll begin
with naturally acquired immunity. So let’s look at the passive form first. So you have
mom who gets exposed to the invader. So think about the invader as the antigen, and then
mom produces antibodies to that antigen. So now mom gives birth to you. Okay, so when
mom gives birth to you, she passes her antibodies on to you, the newborn child. So I want you
to illustrate on the graph below how you think the level of antibody would change in the
newborn over time. So I’ll give you a few seconds to do that. If you want to pause the
video for a moment to have more time to think about how the antibody level would do over
time, please do so. What we’re going to do—and we’re going
to think, “Okay, let’s look at our axis.” Time is on the X-axis and antibody level is
on the Y-axis. So when mom gives birth to you, your antibody level is going to be high
at birth, right? So you can about time zero as birth; so that antibody level will be high.
Now you have never been exposed to this antigen, so your body has no memory cells. It has no
B cells to this particular antigen. So over time, that antibody level is going to drop.
Antibodies don’t live forever. So that’s a passive naturally acquired immunity. It’s
naturally acquired because you were naturally given those antibodies from mom because she
was exposed to the antigen. Now we move on to the active naturally acquired immunity.
So an active naturally acquired immunity— now we’re going to leave mom behind. We’re
not going to worry about mom and pregnancy any more, now we’re going to think about
you yourself. So you’ve acquired the invader, so you’ve
been exposed to the antigen, and then you make antibodies to the invader. So if you
survive, this is actually the best form of immunity is to get exposed to it and build
up your own immunity to it. So now what I want you to do is to illustrate on the graph
how your antibody level would change over time once you’ve been exposed to this particular
antigen. So again, if you’d like to take a moment to do this, pause the video and then
play the video again and you’ll get the answer. Your antibody level is going to start
off low. We’re going to start off at time zero where you don’t have any antibodies
yet to this antigen because you haven’t been exposed. Once you become exposed, your
body’s going to produce those antibodies. Remember that the first response, the first
time you’ve been exposed to the invader, it’s going to take you seven to 10 days
to make antibodies. So your level goes up and it kind of plateaus, right? Now if you get exposed for a second time,
then this antibody, do you think it will go up or go down if you get exposed to the same
antigen for a second time? Hopefully you said it would go up,. So then eventually this level
plateau, and then eventually it’s going to start to decline a little bit, okay? Because
again, those antibodies are not going to survive forever. However—this is the catch—in
active immunity, you have memory cells. So if you are ever exposed again, you can easily
and very quickly make more antibodies. Remember in the passive form, you do not have any memory
cells or plasma cells for that matter, because you weren’t actually exposed to the antigen. Okay, so blood types are actually a form of
natural immunity. And in lab, you have already experienced these various blood types. So
be sure that you can go through and you understand how blood types are a form of natural immunity
and all the information that we did in lab is the same information that’s here. Be
sure you know this material. If you need some help, please come see me. Okay, so now we
move on to artificially acquired immunity. So the same thing holds true. We have two
different types—we have passive and we have active. So let’s look at passive first. So in passive, there’s a serum containing
the antibody and you’ve been injected with it. So you’ve been injected with an antibody.
You’ve never been exposed to the antigen, but you’ve been injected. So now please
pause the video and illustrate on the diagram how you think your antibody level would change
over time if you were injected with the antibody. So your antibody level would start off high,
correct, because you’ve been injected with it. And then over time it would decrease,
okay, because again, you haven’t actually been exposed to the antigen. So you would
never make any plasma cells, you would never make your own antibodies, and you would never
make any memory cells. Then there’s the active form. Active is where you’ve actually
now been vaccinated, and you’ve been vaccinated by the nonvirulent form. What this means is this is supposed to be
the form of the antigen that does not make you sick, but it does stimulate the production
of antibodies by your body. So you’re going to man an immune response and you’re going
to make antibodies. So now indicate on the graph when the first vaccination and when
the booster was given, and then why should a booster be given. So the first vaccination
here, and then over time, we noticed that the antibody level dropped and then it went
back up. So the point at which the antibody level went back up must be where you were
given a booster. So notice how much more the antibody level increased when you gave a booster.
So it’s a very good thing to give a booster, okay? Your antibody level goes up that much
more and you produce more memory cells. Now we also have immune dysfunctions and one
of those are allergies, which a lot of us suffer from. So allergies are actually hypersensitivity
reactions. And when you have a hypersensitivity reaction, you’re going to have an increase
in immunoglobulin E. Now the most serious consequence of an allergic response is the
fact that when we have IGE antibodies being produced, that can cause your mast cells to
secrete histamine.

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