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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

21. The Immune System

The Innate Immune Response



Innate Immunity

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Hi in this video, I'm gonna be talking about the innate immune response. So remember the innate immune response is going to be the first response. It's much more simple. But essentially there are three components, the innate immune response. The first are chemical and physical barriers, which I'm not going to talk about because they're just kind of common sense. Right? These are the skin acidic ph of the gut sort of enzymes or proteins in the mucus that can degrade bacteria or harm viruses or you know, get rid of these pathogens before they can actually infect cells and cause harm. So those kind of makes sense. Then we have the second response and these are the cell intrinsic responses. So these are responses that this one cell. So a single cell can do to stop the pathogen. And then finally you have a specific cells. So these are very similar to the cell intrinsic responses because usually specific cells are one cell but usually there's collections of fig acidic cells which go travel around the body and um you know, can be activated and activated other cells to destroy the pathogen. So here's just an example of a blood sample. So you can see the blood cells here. So these little, I don't know, doughnut looking things or blood cells. But you see all these other things in the cell as well. And these can be these are, you know, part of the innate response. Their specific cells, their white blood cells, There are things that are coming in recognizing pathogens and stopping the infection. So what happens after the body is presented with some type of pathogen or infection. So after the infection there are multiple components that come together to initiate the innate immune system response. So the first thing that's really important in the innate immune system response are these things called pathogen associated molecular pattern patterns we abbreviate, this is champs. So pants are actually sequences um on the infection itself the host cell recognizes. So a lot of bacteria some viruses they have have these things called pants. Which are very similar across all of one species of bacteria. All of these one class of virus. So the emei immune response which is not a very specific response. It's kind of just this like all out response but it can recognize these pants because they're similar on so many different bacteria. And so the things that recognize these pants are called pattern recognition receptors. So these are on the surface of the innate immune system cells and they can bind to the champs and they say okay here's the pathogen because our body doesn't have any pants. So if I if I if I experience the champ then it must mean that I'm interacting with the bacteria. So an example of this is called the toll like receptor. This is the most common example. You'll see um and the toll toll like receptor of the T. L. R. When it combined to a champ this is going to initiate this innate immune response. So signaling is going to be activated, it's going to be activating cells, cells are going to start toasting things and the innate immune response is going to be really like highly up regulated. So um once the pathogen, once the pants are bound to the receptor this can stimulate the cell to kill the pathogen it can activate other cells um and eventually lead actually to the adaptive immune system response. But I'll talk about that more in a second. So here we have an example of a toll like receptor. So you can see toll like receptor TL four. So if an anti gen say this bacteria binds this toll like receptor then this can signal all of a bunch of different downstream pathways in the cell and all of these pathways are immune system components. They're all going to activate the cell to do something to stop this pathogen either by initiating that pack of psychosis, initiating the release of chemicals that will activate other pathways or the adaptive immune system. Um And I'm not going to go into the specifics and you definitely don't need to memorize these pathways or understand what these abbreviations are. Just understand that you know some type of pathogen interacts via the T. L. R. Which is a pattern recognition receptor because of the pants that are present on a lot of different bacteria that activates the cell to do a lot of different things. Now there are other components of the innate immune system that that's in addition to these pants being recognized by things like toll like receptors. So this includes the complement system. Now the complement system is a collection of around 20 proteins that just always are circling in the blood. Now if you get an infection these proteins then become activated and can help get rid of the pathogen. Now these there's a lot of different nuances with the complement system but I'm gonna say that for your immunology classes but just know recognize this term. No the complement system exists and that it can help get rid of pathogens. Then we have these fake acidic cells which find engulf and destroy the pathogen and then we have this special type of cell called natural killer cells which do exactly what you think they do. So natural killer cells sort of survey the whole body and when they encounter a cell that's been infected with bacteria or a virus they will say oh my gosh you're infected So you need to undergo a popped oh sis and kill yourself because when you undergo apoptosis and kill yourself you're also going to kill the pathogen. And so it's kind of like killing oneself for the sake of the whole body. Um which natural color cells are great at doing So they recognize the infected cells and they stimulate those infected cells to kill themselves in the pathogen. So here's an example of the compliment system. So what you can see here is there's an an engine, it's yellow here. It's being recognized by an antibody. This actually isn't required. An antibody doesn't need to recognize it because that's part of the adaptive immune response. Not DNA but it doesn't really matter how this is initiated. But what you see is there's an anti gin. So this is some type of pathogen here and so then we get the complement system which you can see here. C one, C two, A C four. You don't need to know all of these terms or proteins or anything but anywhere where you see a C. One or C. C. And then a number. These are all proteins in the complement system. And you can see that they all become activated in various ways. They travel down all these different pathways activated. But eventually what happens is the cell is gonna swell, it's gonna burst, it's going to kill this and again um in some way. So but this one showing the cell swelling and bursting. But compliment can also do other things and stimulate the cell to kill itself or stimulate the release of things that will kill the cell. Um But essentially the complement system is another innate immune response because it's not specific, right, This is any pathogen here, all of these proteins will become activated when it starts being specific. That's the adaptive immune response. And then finally just some last little bit tidbits about the innate immune responses deals with inflammation including pain. Heat swelling at the infectious site will help get rid of the pathogen by heating it to certain levels by letting you know you have an infection. Um and by swelling to bring in those white blood cells that will host it. And then finally the N. A. Immune response is the one primary way that the adaptive immune responses actually activated. So an important cell here that I'm going to talk about later are dendritic cells. And they have these T. L. R. S. Which remember these pattern recognition receptors. They recognize champs they can bind to the pathogen, activate the N. A. Immune response but then go on to activate the adaptive immune response. So these are connected very intricately through these sort of mediator cells. Dendritic cells are a good example of it but like I said I'll talk about this sort of connection between the two systems and further videos. So with that let's now move on.

Which of the following is not an innate immune response?


What is the name of the pathogenic sequence that a host cell recognizes as foreign?