Innate Immunity

Hi. In this video, we'll be talking about the innate immune system, your body's first line of defense against pathogens. Now the innate immune system is going to amount a non specific response, and that's supposed to as opposed to the specific response that the adaptive immune system will launch. The skin is basically the front lines of your body's defense systems. It's sort of like the moat to the fortress, and it's gonna protect the inside of your body from any pathogens that might want to enter. Of course, it's an imperfect barrier. Not only are there holes in it like you could see this nostril right here, but it can be penetrated in other ways. It can be broken open through physical injury, allow allowing pathogens in. So it's the front line, but very much so, not the final line of defense. Now all of the openings to your body well generally have Cem mucus surrounding them, and this is a slimy secretion that is a mix of Polly sack rides and water, and its purpose is to trap foreign invaders. So, you know we have mucus in our nostrils because that's an opening to the outside. We could potentially breathin pathogens like you see happening here in this image. So the goal is that if we do breathe in some bad stuff, it's just gonna get stuck in our mucus, and then we will expel it like you see this guy doing here. It's worth noting that mucus also can contain anti microbial enzymes, So not only will it trapped those invaders, but it might actually kill them while they're trapped. Kind of like a roach motel. The pathogens check in, but they don't check out now. You will also find what are called leis designs, which are enzymes that breakdown bacterial cell walls. And you'll find these associated with tissues, Uh, that you can have pathogens entering from the outside. So it's just another sort of non specific defense, uh, in these vulnerable areas of the body. Now the innate immune response is going to be that first response to pathogens. It's going to be initiated by Lucas sites, which are those white blood cells. And again it's going to be non specific, as opposed to the specificity of the adaptive immune system. Now, since it's not even though it's not specific, the immune cells have to be able to recognize the pathogens. And they're going to do that through what are called pathogen associated molecular patterns or champs and basically thes air just molecules that are commonly displayed by pathogens and will not be displayed by human cells or cells of the organism's body so that it knows their foreign. A perfect example of this is the Lippo Polly Sack rides that you find on the surface of bacterial cells. You can see one right behind my head here, and basically this is going to be just one of those pathogen associated molecular patterns not super specific, you know, like lots of different types of bacteria are gonna have these, but it's a way to tip our immune system off that. Hey, there's some bacteria hanging out here. So how does our immune system recognize it? Well, our immune cells will have what are called pattern recognition receptors that air membrane receptors that identify those pants. So these PR ours are going to identify the pants and a specific type of pattern recognition receptor that you will see in a lot of immune cells. Are these toll like receptors, as they're called? Were T. L R's and again those air type of pattern recognition receptor that air found on some immune cells. And what's special about them is they will initiate a signaling cascade, which will help recruit other immune cells and lead to a mounted immune response. One specific type of toll, like receptor T L R four recognizes those, uh, Lippo Polly Sacha rides from bacteria those pants that bacteria have and it will release site of kinds. In response. Thio binding with the Lippo Polly Sacha ride. And those CIDA kinds are signaling molecules that will attract other immune cells and help mount the immune response. And you can see those t l R's right here. Uh, this is our cell membrane there, protruding out from the cell surface and they will bind, you know, the Lippo Polly Sacha ride. That's what the LPs is right there. They're gonna bind that Lippo Polly Sacha ride that is expressed by bacteria. And that binding, as you can hopefully see, will initiate uh, you know, a whole cascade of responses within the cell that ultimately will lead Thio, for example, releasing those cited kinds with that. Let's flip the page

one of the main weapons that the cells of the innate immune system have against pathogens is fake Rosato sis. It allows them thio remove these pathogens and prevent them hopefully from infecting any cells. Now they're gonna be three types of cells that will be performing fa grow site Asus in the innate immune system those air neutrophils which are faggots sites or cells that perform Fabbro psychosis that will circulate in the blood. And they're going to be attracted to infected tissues by CIDA kinds those messengers sick or those messenger molecules, those chemical signals that will attract cells of the immune system. So if I jump out of the way here, you can see a neutrophils circulating in the blood. Here we have, ah, red upset a red blood cell, and it's gonna circulate in the blood and look for these site of kinds and it's gonna be attracted to them. Go in. Look for those pathogens that you can see here. That's a pathogen, and it's going thio bagasse a toast them it's gonna eat them up, and you can see what that faggots ketosis kind of looks like here. The cell will actually pinch its membrane around the thing it's trying to engulf and basically suck it in in a vest sickle. And here in this particular cell, it's actually going to digest what it takes in and break it down like you see there now, neutrophils are kind of like the mobile warriors. They're gonna go seek and destroy these pathogens. But macrophages, arm or like defenders, they kind of hang out in tissues and organs that will frequently encounter pathogens. Uh, and there mainly be found around like the lymphatic system and especially lymph nodes, because they're gonna be a lot of pathogens that cycle through there. And in addition to macrophages, you'll find dendritic cells in those areas to. And these dendritic cells are also faggot sites, except their job is a little different. They aren't there, just thio remove. You know, the pathogen they find like, for example, the macrophages. Its job is just thio gobble up. Uh, any pathogen it finds like Here's the bacteria. It's going thio. Gobble it up, Remove it. Dendritic cells are there to actually take what they, uh, faggots chitose and use it to stimulate the adaptive immune system. So their job is super important because they're going to bridge the innate immune system and the adaptive immune system, and they're gonna help trigger an adaptive in response. So these faggots sites are not the Onley in eight remain responses are body has some other tactics they can use. Um, you might not think of it because, you know, we tend not to deal with this in our day to day anymore. But, you know, we used to have to worry about parasites much more often. We actually have these immune cells called you sign a fills that are there to defend against multi cellular parasites. And we also have some defenses against viruses. There are these cells called natural killer cells. Super cool name. They circulate the body and they destroy viruses. I triggering a popped Asus, which is programmed cell death. And I jump out of the way here. You can see, uh, the cells of our body will basically present certain things on their cell surface that allow our immune system thio, identify them as self as as part of the organism. So, you know, like don't hurt these guys. These are the good guys. So here we have a natural killer cell and it's checking out this guy basically saying, Okay, you're all right here. We have a cell infected with a virus and that is going to be terminated by this natural killer cell. It's gonna trigger apoptosis and cause that cell tow lice or break apart. And it's going to do this because it's going to be able to detect whether or not the virus is in there, uh, in a system that we're actually going to cover when we talk about adaptive immunity. So I'm not gonna really get into the details now. Needless to say, these natural killer cells can identify cells that are infected with viruses and will destroy them. Now ourselves will also secrete these special cited kinds called interference. And these will actually induce, uh, induce cells. Thio interfere with viral replication in various ways. Now, lastly, wanna talk about this basically system of proteins called the Compliment system? These proteins will be found in the blood, and they're activated by those pathogen associative molecular patterns. They're also activated by antibodies, and we'll talk about this again when we cover the adaptive immune system. I just want to point out that they're not exclusive to the innate immune system. However, they are part of the innate immune system because they can recognize those pathogen associated molecular patterns. And what they're gonna do is basically put holes in the membranes of these pathogens and cause the cells thio lice and you can see the complement proteins here. Basically, they'll form a poor that will, uh, stick through the membrane of the pathogen and, you know, cause it thio break open. You know, you'll have a bunch of these poor swarming in the membrane of the pathogen, and it will just explode like you see going on here with that, let's flip the page.

The inflammatory response is a special type of innate immune response that will result in swelling of region. So if, for example, you fall and scrape your knee, let's say following that injury, platelets are going to form clots to seal off that site and prevent blood loss, and also hopefully, prevent any nasty stuff from getting into the wound. Now those wounded tissues and the macrophages around them are going to release chemical lines, which are basically like a special type of site of kind that recruit cells to the infection site. Now mast cells, which are a special type of immune cell there type of granule site. Their main job, or one of their main jobs, is to release histamine, and this is a chemical signal that's going thio constrict blood vessels in the area. And that's going to not only reduce blood flow to the area but also prevent blood loss from the area and part of uh, part of mass. ALS. Job is also to signal the peripheral blood vessels to the infection site, so you know the local blood vessels are gonna constrict. The blood vessels in the area around that are actually going to dilate, and that combination of dilation and the chemo kinds that air being secreted is a major signal to neutrophils to, like mobilize, get there right away and go to that infection site and deal with any pathogens there. Macrophages will also actually be recruited to the infection site and really cited kinds to recruit MAWR immune cells. So hopefully you can see that immune responses are sort of like escalations. You know, there's an initial signal of, like help bunch of immune cells move in and you know, they kind of shout, help and mawr guys come in and the the signals and the response grows and grows. It's an escalation to recruit more and more cells to that area to deal with any pathogens or any infection. And here I'm trying to you sort of cheap and use the same figure. But pretend that this time you know these are histamines and also cited kinds and stuff. I don't have a great image. Unfortunately, Thio illustrate the inflammatory response, but it's a very similar process and and this is really a theme you'll see throughout the immune system is cells secrete ing a signal to recruit other cells to that area to mount some type of immune defense. So that's all I have for this video. I'll see you guys next time, stay healthy.