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Types of immune responses: Innate and Adaptive. Humoral vs. Cell-Mediated : Overview of types of immune responses. Difference between innate and adaptive immunity. Differences between humoral adaptive immunity and cell-mediated adaptive immunity.
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- In the last video, we talked a little bit
- about the immune system.
- In that video, we focused on the nonspecific or the innate
- immune system.
- So let me write that.
- And even in the nonspecific immune system, we subdivided
- that into kind of the first line barriers.
- And those were things like the skin, or the stomach acid, or
- the acidity of the oils on the outside of your skin.
- These are just natural barriers to not allowing
- things inside of your body, but then once they get in-- so
- you can almost imagine these were the
- first line of defense.
- And then you had your second line of defense, but these are
- still nonspecific-- and when we say nonspecific, it means
- that they don't necessarily know what type of virus, what
- type of protein, what type of bacteria.
- They just know that this thing looks shady.
- Let me eat it up.
- Let me kill it.
- Let me have an inflammatory response.
- So in there, we said, well, there's an inflammatory
- response, which I'm actually going to talk about after we
- do videos on the specific immune system.
- You have your inflammatory response, which really just
- gets things to where the action is at and then you also
- have your phagocytes, which are these cells that are
- engulfing things.
- And just so you know, all the phagocytes that we talked
- about in the last video, these are all instances of white
- blood cells or leukocytes.
- These phagocytes right here, these are all-- I talk about
- dendritic cells and macrophages and neutrophils.
- These were all white blood cells.
- These weren't all the kinds of white blood cells.
- We're about to talk about more-- and the other word for
- white blood cell is also leukocyte.
- So that is nonspecific.
- Well, one, it just doesn't let you in, but then when you're
- in, it says, hey, you're just shady.
- I'm going to eat you up.
- I have receptors.
- You have some double stranded DNA floating around.
- Only viruses have double strand DNA.
- I'm going to eat you up.
- I don't know what type of virus you are.
- I don't know if I've seen you before or not.
- That's why it's nonspecific.
- Now the really interesting thing about our immune
- system-- and this nonspecific, this exists across many, many,
- many species and types of organisms. But the specific is
- kind of a-- it's thought to be a newer adaptation.
- What I'm going to talk about is the specific immune system
- that's particular to humans.
- That's our other classification.
- Let me do it like that.
- So then you have your specific-- or you can imagine
- it's an adaptive immune system.
- You've probably heard of things like that.
- I have resistance to that bacteria or that virus.
- So this is adaptive.
- And it's really all based on having exposure to things.
- And within the specific immune system, we talked a little--
- when we talked about the antigen presenting molecules
- that phagocytes do-- that plays a role in this.
- We're going to go into more detail, but I don't want to
- confuse you.
- But the main actors here are called lymphocytes, not to be
- confused with leukocytes-- because they still are
- leukocytes.
- So let me write this down.
- These are specific.
- Phagocytes, for the most part, are nonspecific, but both of
- these are white blood cells.
- Lymphocytes are another type of white
- blood cell or leukocyte.
- Don't want to confuse you with this convoluted diagram, but I
- just want to make the terminology clear.
- When someone talks about a white blood cell, they're
- really just talking about a set of cells that when people
- first tried to separate the components of blood-- you'd
- have your red blood cells that would kind of settle in the
- bottom, then you'd have this layer of white frothy stuff in
- the middle that was really made of white blood cells, and
- then on the top, you had the fluid, the plasma from your
- blood, kind of the watery part.
- So that's where the name came from, but they have different
- roles, but they interact with each other.
- Now lymphocytes can be divided into B lymphocytes, usually
- referred to as B cells-- and T lymphocytes.
- And the B and T just come from where they're developed.
- B lymphocytes were first recognized in
- the bursa of Fabricius.
- That's why it's called B.
- That's actually a part of birds that participate in the
- immune system.
- And so the B came from bursa, but B also applies to the
- human immune system because it's produced in bone marrow.
- So that might be an easier way to remember.
- It's produced in bone marrow.
- It's developed in bone marrow, but historically, the B came
- from the bursa of Fabricius, just in case you want to know.
- But it's easy to remember.
- The B could also stand for bone marrow because that's
- where it's produced.
- T lymphocytes actually do start off in the bone marrow,
- but they mature and become what they are in the thymus.
- So that's where the T comes from.
- Now in this video, I'm going to focus just on the B
- lymphocytes-- because frankly, if I focused on everything, it
- would be an hour-long video.
- But the B lymphocytes frankly on some level-- well, I don't
- want to pick and choose favorites, but something in my
- brain-- I just really like the B lymphocytes.
- So the B lymphocytes participate in what's called
- the humoral response.
- And I'll tell you what humoral means in a second.
- You'll see that T lymphocytes participate in what's called
- the cell mediated response and we're going to do that in a
- future video.
- They actually do certain classes of T lymphocytes.
- We'll see that there are helper T cells and there are
- cytotoxic T cells.
- I know it's all very confusing the first time you see it, but
- that's why I just want to focus on just
- this part right here.
- We're going to see in the future that the helper T cells
- play a role in amplifying and really activating
- this humoral response.
- But a simple way to think about the difference between
- the humoral response and the cell mediated response is,
- when I get infected-- let's say I get
- infected by a virus, right?
- At first, when a virus comes into my system, it's just
- floating around in the fluids in my system.
- The fluids of our system-- that's really what humoral
- responds to, into the humoral fluids of your body.
- So you have your viruses.
- These are little viruses floating around.
- So while they're floating around and they're not sitting
- inside of cells, that's where the humoral response
- can come into play.
- Same thing if we have little bacteria floating around and
- they haven't infiltrated cells yet.
- They're just floating around in the fluid, then the humoral
- response can be useful for that.
- Now if all of a sudden, these guys have infiltrated cells--
- so if the cells are now infected with the virus and
- they're producing the viruses using the mechanisms of the
- cell to produce more, then all of a sudden we have to be a
- little bit more sophisticated in how we deal with these
- cells and how we deal with the viruses because they're not
- just going to be floating around anymore.
- We probably want to just kill this cell even though it was
- one of our own, but now it's helping to make viruses.
- Or maybe it's been colonized by bacteria.
- So in either case, you want to kill this.
- And we'll talk more about that in the cell mediating.