In this video, we're going to begin our lesson on antibodies. And so antibodies are defined as y shaped proteins that are actually produced by plasma cells and they have the ability to bind very specifically to antigens and generate an immune response. Now, antibodies are also sometimes called immunoglobulins and abbreviated as IG. And although there are five different classes of antibodies that will talk more about moving forward in our course, typically antibodies have the same general structure. And so in our next lesson video, we're going to talk more details about the structure of the antibody. And so I'll see you all in that video.
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concept
Antibody Structure
Video duration:
5m
Play a video:
So from our last lesson video, we already know that antibodies are Y shaped proteins, but in this video, we're going to talk more details about antibody structure. And so antibodies actually consist of four polypeptide chains, two of which are identical light chains or L chains for short. And the other two are identical heavy chains or H chains for short. Now, the light chains are actually much lighter than the heavy chains, which are much, much heavier and larger. Now, these four chains are covertly linked together via disulfide bonds. And so if we take a look down below at our image, notice we have our Y shaped antibody right here and notice that our Y shaped antibody has four polypeptide chains. It has this light chain that is identical to this light chain over here. And then it has this heavy chain uh right here that is identical to this heavy chain right here. And so you can see that the heavier chains highlighted in green are much larger and therefore much heavier than the lighter chains, which are much smaller and much lighter in mass. And also notice that these four chains are covalent linked together via these disulfide bonds that exist between the R groups of cysteine residues. Now, what's also important to note is that each of these light and heavy chains has a variable region, also known as a V domain, as well as a constant region, also known as AC domain. Now, the variable region or the V domain is going to be located at the tip of each of the prongs of the Y and it contains the N terminal end of each of the polypeptide chains. So if we take a look down below at our image, notice that the V or variable domain is highlighted with a green background right here at the tips of the prongs of the Y. And notice that it also contains the N terminal N or the free amino groups of each of the four polypeptide chains just like what we said up above. Now, what's also important to note is that the uh V domain contains the antigen binding site. So this is where the antibody is going to bind to the antigen at these two potential positions indicated by the arrows. And so the reason it's called the V or variable domain is because this region right here will actually vary between different antibodies. Now, the C domain, on the other hand, because it's the constant domain, it's not actually going to vary, it's gonna remain constant even between different antibodies. Now, the C domain is of course going to be the rest of the antibody. So it's gonna be located at the hinge and the stem of the Y. So if we look, take a look down below, of course, the C domain uh is going to be uh the rest of the antibody here. And the C domain is important because it's actually recognized by immune system cells. And so essentially what happens is the V domain will bind to the antigen at these positions And then an immune system cell can bind to the C domain. And so the antibody can act as an intermediate between the immune system cell and the antigen. Now, what you'll notice is in our image here, we have, we have uh the V uh domain uh here with uh the vs on them. And then whether or not they light or heavy chains is indicated by the L and the H. And so, uh you can see that both the uh heavy chain here and the light chain has AAA variable domain as well as a constant domain. And so, uh what's important to note is that we can further break up the structure of this antibody. Uh If we imagine breaking the antibody at the hinge of the Y. And so here in a dotted red line, what we have is an imaginary line if we were to break our antibody right at the hinge. And what that would do is it would leave us with the top portion here, which we would refer to as the FA B region. And this is because this uh has the uh the fragment that has the antigen binding site. So you can see we have the antigen binding site in this region. And then we're also left with the bottom half of the antibody down below uh which would be the FC region or the fragment that contains the constant region. So this would be the FC region, this bracket right here. And so really, this is the structure of a typical antibody. And we'll be able to get some practice applying the concepts that we've learned as we move forward in our course. So I'll see you guys in our next video.
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Problem
Problem
_________ is another name for antibodies.
A
Epitope.
B
Immune protein.
C
Antigen.
D
Immunoglobulin.
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Problem
Problem
An antibody’s variable region:
1. Varies in amino acid sequence to allow different antibodies to bind different antigens.
2. Is located in the hinge and stem regions of an antibody.
3. Is a portion of the light chain of an antibody.
4. Is a portion of the heavy chain of an antibody.
A
1 & 2.
B
1 & 3.
C
3 & 4.
D
1, 2, & 3.
E
1, 3, & 4.
F
1, 2, 3, & 4.
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concept
Antibody Diversity
Video duration:
2m
Play a video:
In this video, we're going to talk about antibody diversity. And so it turns out that our immune systems have the potential to produce an enormous amount of different antibodies, perhaps greater than 10 to the 18th or one quintillion different antibodies. That's more antibodies than the estimated amount of individual grains of sand on our entire planet. That's a lot of antibodies that our immune system has the potential to produce. In fact, there's so many potential possibilities for antibodies that they all cannot be produced in one single lifetime. So here we have a question and it's asking how in the world is it possible that antibody diversity can be so large if humans only have 25,000 genes, which is a much smaller number than one quintillion. And so the answer to this question is actually right here. And so antibody diversity actually results from significant amount of gene rearrangements, splicing and mutations. And so notice down below, over here, on the left hand side, we we what we have is DNA being shown and this DNA is coding for an antibody. And so you can see that the different regions of the DNA are color coded to show you what part of the antibody that they express. And so uh notice that the original DNA up here has many different combinations for these different uh regions of the antibody. However, through splicing and rearrangements, we can get different smaller combinations, combining different features and even mutations in the DNA can create lots and lots of diversity. And so through transcription of the DNA into RN A, you can see that even the mutation will carry over here and then through translation, what we get is the antibody being produced and even a single slight mutation like this one right here can result in a different antibody being produced. And so we get a diverse antibody just through all of these gene rearrangements, splicing and mutations. And so this concludes our introduction to uh antibody diversity. And in our next video, we'll be able to talk about monoclonal and polyclonal antibodies. So I'll see you guys there.
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Problem
Problem
Genetic recombination frequently occurs in the body’s B cell population. Why is this advantageous to the immune system?
A
More genetic diversity in antibody genes creates more diversity in antibodies.
B
Having the ability to produce more diverse antibodies allows B cells to respond to a larger number of pathogens.
C
More genetic diversity allows CD8 effector cells to be able to recognize and kill more endogenous pathogens.