B Cell Development - Video Tutorials & Practice Problems
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B Cell Development
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Hi in this video, I'm gonna be talking about B cell development. So B cells are part of the adaptive immune response and they're super important because they are the cells that produce the antibodies for our body. Now we're familiar a little bit with antibodies we've heard them in terms of vaccination or infections of things. But I really want to talk to you about, you know the cells that are producing these antibodies. So be sales are specific. They're like extremely specific because they produce only one type of antibody for one pathogen. And not only is it just for one pathogen, it's for one small sequence on that pathogen called an antigen. So um in order to have enough the cells, I mean think of all the bacteria in the world we could be exposed to all the viruses. We need antibodies against all of these things. But we not only need one antibody against one small sequence or Auntie jen, we need multiple antibodies from multiple antigens on every pathogen. So every time an antibody is produced that's a different B cell. So they're super specific and that means we need a ton of them ton of diversity. But B cells need to also work correctly and they don't need to attack the host. So this is a property called self tolerance which just means that the B cell produces antibodies that don't target itself. So my B cells aren't going to target my skin or my kidney or my gut or my brain. They're going to say, oh those cells are us and anything else is pouring. And so the B cells have to be self tolerant. They have to recognize what is me and what isn't me. And when these cells fail to do that, this results in autoimmune diseases. So autoimmune diseases are the result of the immune system attacking itself. They've lost the self tolerance. They no longer can tell what is me and what is foreign. And so they just begin attacking everything that's obviously bad. And so we're most familiar you are with antibodies in terms of vaccination. So let me go a little bit and how vaccination works. And it essentially works by activating the cells before you actually need them to be activated. So when you get a vaccine you get targeted against something, we'll just say measles and this initiates a primary immune response. So this is a small immune response that occurs the first time you're ever exposed to something. So, for instance, measles, This also occurs, you know, with a vaccine, then the secondary immune response, This is going to be a much larger and faster response after you during the second or you know, later exposures. So what it looks like when you get vaccinated or when you get exposed to any kind of pathogen really is that the first exposure, this would be the vaccination or the first exposure to something like measles, your and this is the immune system system response. So what you see is that your first exposure happens here, Your immune system is activated. You know, it's producing antibodies, it's producing these cells that are specific towards whatever you are vaccinated against measles. So it's produce some antibodies but it's obviously not a big huge response. It's it's fairly mild. I mean your body can use this to clear an infection, it does it all the time. But if you think if you have something very serious like measles or even, you know, something that's been in the news recently, Ebola, I mean you're not going to really kill this off with something that's really serious. You may fight off the common cold but you're not going to kill a serious disease. But this is the first, the first exposure. So this is why we do vaccination, we say okay, we'll give you a first exposure. So you have this low immune response. Your body has made some antibodies, your body has seen it before and that way, if you're ever exposed to measles or Ebola or whatever. Again, then the immune system is like, oh I got this, you know, I've seen this before, I have antibodies against it and so it has this huge initial response and it clears the infection on me very quickly. So then it goes back down, it's like okay, I got this. So this response here is what you're going to experience any other time you've been exposed to the disease, as long as you know, you've been exposed to previously either through just a regular exposure or through vaccination. So vaccination is really the really activating these B cells so that your body can already have antibodies ready in case you're ever exposed again. But this is a video about B cell development. So let's talking more about how B cells become specialized to produce one antibody. So this is through a process called the colonial selection theory and it explains the maturation of the cells. So what it does. So this is kind of a long explanation. But I'm going to walk through more steps later. The fist theory says that the body creates a ton of the cells. I mean like so many B cells that target pretty much anything you could think of right targets anything foreign. But only a few of these are activated when exposed to that actual pathogen and when um it's activated then those B cells can um amplify proliferate, grow. And that means that the B cells that are really present in the cells. So these collection of B cells are the ones that they respond to the pathogens the body is actually encountered. So let me go through the steps of what this is and that might make it more clear. So the first thing is that there are a ton of B cells floating around in the body. These all produced one antibody um targeting one antigen. But this is before your body has been exposed to any kind of pathogen. So these are the B cells you kind of start with and he says I don't know what I'm going to be exposed to but here's all the B cells that I can make and they're called naive cells because they haven't been exposed to anything. And so they're just like I don't know if I'm going to be activated but then you encounter a pathogen some type of something. So the B cell that responds to this pathogen or the multiple B cells with multiple antibodies that can respond to this pathogen do they respond to it and this becomes activated? So now we call these B cells affect our cells because they're activated and they can begin affecting the infection. So once they are activated they proliferate and make copies a ton of copies of themselves to make more antibodies. So then when you have a lot of copies of this B cell they're producing lots of antibody against the pathogen and they targets it for destruction. And then after you've destroyed the pathogen, most of these B cells die off because you don't need them anymore. You don't need to be producing wasting all that energy producing a bunch of antibodies against the pathogen you don't have. So most of the B cells die off but some of them actually travel to the bone marrow and become memory cells and these are exactly what they are. Sounds like. You know they continue producing that antibody at low levels they're there in case you ever expose that pathogen again. Um and they're you know just stored in the body so that if any time you were to present this pathogen again they would be able to be used to fight off that pathogen. So here we have an example of B cell development. So we start off with the B cell is activated by some pathogen. Um It then um will actually digest this pathogen so that it can activate different parts of the immune system but also mature into effect er cells and stimulate antibody production. Now there's a lot of words here I we'll go over this actually in a different topic a little bit more. But for now what I want you to see is that the B cell is interacting with the anti gen it will eventually become this effect er sell produce a ton of antibody and then a few of them after the infection is past will become memory cells. So that is how B cells mature and produce specific antibodies to target infection. So with that let's now move on
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Problem
Problem
Each B cell produces only one antibody which targets only one pathogen.
A
True
B
False
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Problem
Problem
A B cell that becomes activated in response to a pathogen is called what?