so let's let's go ahead and start chapter 15 so remember chapter 15 we're studying the immune system right the immune system and chapter 15 and 16 are about the immune system also known as host defense okay now with chapter 15 we're going to talk about the first two lines of defense that we have we have first line defense and second line defense against microorganisms and then the chapter 16 is going to be more about our third line of defense we have against microorganisms okay so let let me explain these lines of Defense real quick the first line of defense is as it sounds what keeps you pathogen free what what is the first what is your first defense against pathogens your skin right your skin is great at keeping pathogens out it's a physical block right to invasion in addition to your skin you also have all these fluids and mucus right you got mucus membranes you got tear you've got ear wax you've got saliva you've got all kinds of other mechanisms as well that are part of your first line of defense you got your stomach acid you've got your if pathogens make it into your lungs you've got the mucco ciliary blanket you know the little cyia that beat to get stuff out of your lungs all this stuff is your first line of defense okay and that's part of chapter 15 okay next we got the second line of defense let's say things get into your system the germs get into your fluids right your blood inside of your tissues your organs where they shouldn't be now it's time for you know the second line and the second line these are the you know the protective cells and fluids that are nonspecific so what does that mean that means that this part of your immune system is not uh it it reacts the same way every time it it's not specific to a particular virus it knows how to stop viruses in general so if it s so you see the difference instead of just instead of just recognizing this species it just recognizes bacteria right so it's not a specific defense it doesn't improve with time right this is known these two here the first and second line are known as your innate defenses your innate immune system also known as the nonspecific immune system you know why because it's a very general immunity it does not have specific targets it doesn't have a memory right it it it works the same today as it will tomorrow right it doesn't get better with time whereas the third line of defense this is going to be the topic of chapter 16 this is where we have specific immunity this is this is where we have unique prote Ive substances like for example a specific antib against a specific antigen right this is the reason why your immune system improves as you get older right this is the reason why you can't catch the same germ twice usually this is the reason why vaccines work it's the third line of defense it's a specific specific antibody to a specific receptor right does that make sense so so these three in in tandem they work together to keep you safe these are the innate immune system here this is called the acquired immune system here or specific immune system here okay again third line is known as acquired or specific immunity the first two lines are called non-specific or innate immunity the one with born we the one you're born with yeah the one you're born with is innate and then upon each time you get exposed each time you get exposed to a new pathogen or vaccine or substance you build your acquired immunity you build this this builds over time and improves over time these function the same way over time right you see that's why chapter 15 is about the first two and chapter 16 is about the last one okay but they all go hand in hand to keep you safe they all go hand in hand to keep you safe over time we come like resist that's how you become resistant to germs all of these things need to be working in concert right so you see here the first line is part of your innate immune response the first line and the second line the first line remember it includes your physical barriers even your microbiota remember I said you have these helpful back microbes and your gut lining even they are helping to be a physical barrier because without them things like sea could take over chemical barriers remember I told you about this your tears your ear wax your stomach acid even your Sweat Right all of these things are antimicrobial right but if you pass the first line we enter the second line again which is part of the innate immunity this includes phagocytes remember these are the white blood cells that can phagocytose they can engulf foreign Invaders so the phagocytes include we're going to talk about this but they include neutrophils macras dendritic cells right these are all part of the innate immune system and then inflammation right inflammatory response that's a part of the innate immune system fever other antimicrobial products like enzymes or proteins as well okay so all of these are part of the innate immune system they don't have a memory they don't improve with with each exposure to a pathogen right they function the same way uh today as they will tomorrow right however the third line of defense is called acquired immunity or specific immunity this is the one that has specific host defenses that must be developed for each microb through these specialized white blood cells and you know which specialized white blood cells they're referring to the B cells and the t- cells if you've ever heard of B cells or T cells that's the realm of the acquired immunity that's their realm okay so chapter 16's mainly going to be about B cells and T cells whereas chapter 15 is going to be about all the other white blood cells okay yeah you you added fever to eat I don't get that well fever is a line of defense when your body enters a fever State um it is antimicrobial in its nature it it prevents microbial growth uh fever in and of itself is microbiostatic it prevents microbial growth so when your body triggers fever your body wants to have fever your body triggers fever when you have an infection um it's resets your hypothalamus to a higher setting right and so by having a higher body temperature it actually helps sequester iron in your blood your blood becomes hypo foric and when that happens it's harder for microbes to gain access to iron and it actually helps prevent the spread of germs yeah it's pretty interesting so yeah it's part of the innate immune system for that reason so again Immunology is the study of the immune system and these three lines of Defense we're studying all the different white blood cells the white blood cells are involved in the immune response and what is the job of the IM of the immune system is to surveil for pathogens or foreign entities recognize foreign material destroy foreign material that's the job of a healthy immune system and we're going to talk about this in a lot more detail this is what those fosic cells do by the way this would be an example of a fosic white blood cell remember neutrophils macrofagos dendritic cells they have receptors on their surface see these little things that look like little y's these little receptors are known as prrs or pattern recognition receptors these receptors recognize very cookie cutter patterns that are frequently found on pathogens okay so for example do many pathogens have peptidoglycan on their surface bacteria right bacteria have peptidoglycan on their surface right right so is that a common uh pattern so there so your white blood cells have receptors that recognize peptidoglycan right and that's that's a very good pattern to recognize because if you have any kind of bacteria you're going to recognize that peptidoglycan right and so again the receptor is called the pattern recognition receptor and it recognizes what patterns right like peptidoglycan those patterns are called pamps pathogen Associated molecular patterns pathogen Associated molecular patterns what are the pamps what was the one I just gave you peptidoglycan there are more pamps for example flagin you know the the flul it is recognized as well as a pamp right so there is a pattern recognition receptor for flula there's a pattern recognition receptor for Pepto glycan there's a pattern recognition receptor for other common structures on the surface of pathogens you don't have to be a specific pathogen to be recognized you just have to have one of these common structures on your surface okay and so what happens when a receptor recognizes a pattern or a pamp it triggers phagocytosis the plasma membrane wraps around internalization as a food vacu you fuse the food vacu with the lome and what do you think happens you digest the pathogen so fagos sites recognize patterns called pamps with their pattern recognition receptors they then phagocytose that foreign material whether it is a virus or a bacterium it will then digest that virus or bacterium okay and that's their job that's what the white blood cells do uh or the fosic white blood cells and this is all part of the innate immune system okay so again what did the white blood cells tasked with searching throughout your body looking for potential pathogens to destroy right should these white blood cells be able to identify self that means your self well they shouldn't respond to yourself should they right they should be able to recognize self from non self right because do you want to attack self and Destroy self no that's called an autoimmune disease right so an autoimmune disease is when your white blood cells they're seeing your own cells like your own liver and thinking it's foreign right thinking it's a intruder and trying to attack those hepatocytes attack attack the liver right a healthy immune system recognizes self from non self right it should not kill your liver it should kill the bacteria in your blood right it should distinguish between self and non-self if it recognizes self as foreign this is what happens when you get autoimmune disease when your own tissues are being attacked okay now what are the what are these white blood cells actually detecting they're detecting molecules on the surface of the pathogen right these molecules are called antigens think of antigens as molecules that can be recognized by the immune system what's a self antigen that means a a molecule that's common in your body right what's a foreign antigen a molecule that's foreign to your body bacteria are covered in foreign antigen foreign molecules right your cells are covered in self antigen so again healthy white blood cells they don't attack cells exhibiting self antigens they attack cells exhibiting foreign antigens because antigen just means a molecule antigen just means something that can be recognized right Like A protein that could be recognized right if it's a self protein a self antigen shouldn't trigger an immune response foreign antigen like pepo glycan should trigger an immune response that's a healthy immune system and antigens can be composed of proteins they could be sugars but the best antigens are proteins the best the the the immune system is very good at identifying foreign proteins foreign antigens antigens are molecules that can be recognized by your immune system and these could be self antigens which the immune system should not respond to and foreign antigens which the immune system should respond to an antigen could be any molecule on the on the pathogen any molecule and those molecules are usually proteins or sugars because that's what you most cells have on their surface most cells have proteins and sugars on their surface okay okay we already talked about this foreign substances should be recognized and dealt with if if self if self antigens are attacked this leads to autoimmune disorders such as rheum C arthritis this is when the body attacks its own joints and tissues and there are many different types of diseases that are actually examples of autoimmune disorders and again remember the fosic white blood cells have receptors called patterned recognition receptors right they've got these receptors and th those recognize what the pamps right the pathogen Associated molecular proteins right or pathogen Associated molecular patterns on the surface of pathogens so an example of a pamp an example of a pamp is peptidoglycan and that would be recognized by a receptor on a fosic white blood cell right okay I'm G to skip this actually the lymphatic system did you know you have an entire circulatory system in your body that's has nothing to do with blood it's your lymphatics right so you have lymph nodes connected by lymph ducts and fluid flows through these lymph ducts and lymph nodes but that fluid is called lymph fluid and that lymph fluid is basically white blood cells antigens it's a meeting place for antigens and white blood cells and this begins as Tiny capillaries transporting lymph fluid to the lymph nodes and leads to Major vessels that drain back to the circulatory system so there is a cross talk between your circulatory system and your lymphatic system there is a cross talk but they are their own systems and it's pretty neat okay again what's lymphatic fluid it's the fluid that flows through the lymph Network the lymph nodes the lymph ducts the lymph vessels this lymph fluid is called lymph it's a plasma likee liquid and it contains white blood cells and antigens it can also transport fats cellular debris other infectious agents again it's a great opportunity your lymph is where foreign antigen will meet it will likely meet a white blood cell right to be eliminated this is why for instance if I have a if I have a uh ear infection if I have an ear infection the closest lymph node would likely swell right the closest lymph node would likely swell if I have an ear infection why well because these white blood cells that are traveling and this lymphatics are going to sense this infection and they're going to proliferate and they're going to send cells over and there's going to be a whole battle that goes on between my white blood cells and those pathogens in close by so yes because the lymph nodes and the lymphs this is where the white blood cells congregate these become inflamed right these become swollen during an infection because one thing that happens during an infection is white blood cells proliferate right the B cells and the t c cells proliferate and when they do that they make the lymphs bigger the lymph nodes bigger okay again here we could jux the pose see on the left you have the circulatory system with you know uh arteries and veins right transporting blood away from the heart towards the heart and on the right you have a whole another circulatory system the lymphatic syst system and see all these little there's nodes nodes are like big nodules and then there's ducks ducks link the different nodes to one another and lymph is What flows through this network lymph is what's flowing through these green vessels here on the right okay and so again it has a whole another function your circulatory system is to transport oxygen around and things like this your lymphatic system is to transport white blood cells around right and give them a chance to find antigens to attack foreign antigens to attack and you see these are showing you where the nodes are see inguinal nodes pelvic nodes uh you've got cervical nodes uh thoracic nodes these are where these are places where the doctor might touch to see if they feel an inflamed lymph node right a swollen lymph node because the only reason for you to have a swollen lymph node is if you have an active infection somewhere right and usually the infection is somewhere close by to where the inflammation is unless it's a systemic infection in which you're going to have a bunch of inflamed lymph notes so what are the lymph oid organs okay these are organs that perform lymphoid functions they have something to do with you know your immune system the primary lymphatic organs are known as the red bone marrow and the thymus so you got bone marrow right I told you guys about your bone marrow that's a very special site because it houses these stem cells these stem cells are called hematopoetic stem cells hematopoetic stem cells are the stem cells that give rise to your blood so if you if your body needs more blood your bone marrow makes that blood okay and it doesn't it doesn't matter if it's red blood cells white blood cells they all originated from your bone marrow the the stem cells in your bone marrow okay and by the way we're going to mention this again we're going to mention this in chapter 16 but um there are white blood cells in your body called B cells and then there are white blood cells called t cells okay we're going to talk about those a lot but one thing you should know is not only are B cells and T cells they're born in the bone marrow right but B cells mature it's called maturation B cells mature in the bone marrow T cells mature in the thymus the thymus is a butterfly shaped organ in your throat region okay B cells mature in the bone marrow t- cells mature in the thymus um but both of them originate from the bone marrow right in fact all your blood cells or originally came from the bone marrow and what are secondary lymphatic organs these are places where those B cells and those t- cells hang out okay lymph nodes the spleen the spleen is actually a great hangout location for B cells and te- cells they live in the B cells and the I mean the they live in the spleen salt malt and Gul these are just lymphoid tissu so salt is skin Associated lymphoid tissue gut Associated lymphoid tissue there's there's a bunch of them there's there's basically where is the lymphoid tissue close to is it that near the skin is it near the gut there's a bunch of different locations Mal malt what does it malt is I want to say mucus but I is it muc yeah mucus Associated lymphoid tissue so there's all there all kinds of lymo it just means it you see the lymphoid the lymph nodes and all if it's close to the gut it's GT it's the gut Associated lymphoid tissue it's if it's close to the skin it's salt it basically just means your lymphatics right it's your lymphatics and this is your thymus right where's it I why is it well here it is it's a triangle shaped a triangle shaped uh butterfly-shaped organ right in your in your lower throat chest upper chest area all right we might as well go ahead and start real quick I pulled up the YouTube channel because there's some helpful videos on here if you go to the main YouTube channel and then you go down [Music] to Concepts explain this is a playlist called Concepts explain right here see if you click on that there's like a list of different videos and at the bottom these are some good videos here um and some that you may want to know are these ones here like this one here called how natural killer cells work that's a good one because uh natural killer cells are part of the innate immune system mhc1 versus mhc2 explained that's uh important to the immune system and I don't know why but there's two of these um or it's duplicated so I'll try to remove one of them but that's the same thing antigen presentation via mhc1 and mhc2 explained um antibod well this has to do with chapter 16 but chapter 15 has to do with these videos up here okay um yeah so if you want to watch those and summarize them then they'd be good for two points a piece if you want to do bonus right like bonus stuff so watch and summarize and by summarize I mean draw it out and lab you could draw it out label how natural killer cells work mhc1 versus mhc2 uh no need watching both of these are both the same right antigen presentation helper te- cells and B Cell Activation and antibodies explained right all of these are good there's what five videos then one two three four five right because these are double so that's 10 points of extra bonus that you could earn by watching and summarizing those videos and those videos will help you with chapters 15 and 16 yes so just draw the picture yeah draw the picture and label yeah draw and label yep and then turn in those drawings um you know whenever you have a chance you know I I don't have a firm due date on those okay and they will help you to understand better how the immune system works these videos will help you to understand exactly what your B cells are doing what your t- cells are doing what your natural killer cells are doing doing what antibodies are that kind of stuff it's good stuff to know and remember just go to the main YouTube channel and click on Concepts explained and then scroll all the way down that's how you find those videos awesome so let's keep going all right let's keep going so again remember there are these fagos sites and I don't know why they don't list all of them here there's neutr monocytes macrofagos and dendritic cells remember dendritic cells is another one that's here too those are the main types of phagocytes neutrophils monocytes macrofagos and dendritic cells I don't know I think uh they left that out for some for some reason they forgot to add it but it's important to add remember I told you what neutrophils do they they they float around in the blood and in the lymph and they go to sites of inflammation in fact they're kind of like First Responders when there's inflammatory response the neutrophils move to the sight of the the damaged tissue and you you can imagine why right if there's damaged tissue there might be Intruders like bacteria or viruses so once the neutrophils get to the site of the damage they start to phagocytose those Intruders a common sign of bacterial infection is a high nutrifil count in the blood if you have lots of nutrifil in the blood higher than normal this is a sign of a infection it is also the primary component of pus if you see pus from a wound pus is mainly nutrifil dead and alive nutrifil I told you about eosinophils too right the eosinophils they are not fosic but they are defensive white blood cells they kill helmets and protozoa they are attracted to sites of parasitic infections right the parasites worms or protozoa and then they release they release their granules to kill that parasite now monocytes remember monocytes are transformed into either macrofagos or dendritic cells after a short period of time okay and look what it says at the bottom here it says not only are macras and dendritic cells for that matter Dynamic scavengers but they also process foreign substances and prepare them for reactions with B cells and te- cells so we're going to learn all about this when we learn about a concept called antigen presentation it sounds fancy but it's actually really neat it's a link between the innate immune system chapter 15 and the Adaptive immune system chapter 16 there's like a handshake that happens between the two there's a link that happens between the two and that link is called antigen presentation so something that the macras and the dendritic cells do speaks to the B cells and the t- cells to get them involved right that's called antigen presentation I'll explain antigen presentation in more detail in a in a little bit and it's explained in the videos I just showed you too so let's talk about phagocytosis and the steps of Phagocytosis remember the phagocytes are monocytes dendritic cells uh neutrophils and macrofagos right those are the fosic cells those are the main ones you should remember phagocytosis occurs in steps first is chemotaxis remember what chemotaxis means directed cell movement right cells move towards some kind of attractant right if there is tissue damage over there if the skin is broken over there that's going to send signals cyto kindes remember cyto kindes and do you know what that's going to do that's going to get first of all the blood vessels dilated so more blood gets over there right but also there's going to be a signal that causes chemotaxis of neutrophils mainly neutrophils and what do the neutrophils do they do chemotaxis they go to the sight of the tissue damage does that make sense now once the neutr is at the sight of the tissue damage it's likely to encounter bacteria and things right foreign Invaders and then it triggers what ingestion phagocytosis right phagocytosis and then what's called fagos formation this is when the lome the digestive organel of the cell fuses with the fagos the basically the engulfed bacterium you know now you've got enzymes mixed with bacteria so you destroy the microorganism the bacteria and then you excrete through exocytosis you excrete that waste let's go through this step by step so again the fosite it undergoes chemot taxis it moves to the site of infection and tissue damage it then encounters the bacteria you remember how it has receptors on its surface called prrs pattern recognition receptors that recognize pamps remember p m PS pathogen Associated molecular patterns patterns like peptidoglycan or flatulent you know something that's common on a surface of a bacterium that means the receptor binds to the bacterium triggering what phagocytosis engulfment once you are engulfed the bacterium come in inside of a food vacuum right that's called the fagos the fagos is like a food vacu full of bacteria now what we need to digest that bacteria right so the bacteria F the the phagosome fuses with a lome do you guys remember lomes it's a organel it's a little uh vacu full of hydrolytic enzymes enzymes that break down organic matter right so the lome fuses with the fagos kind of like this this is the lome full of enzymes this is the phagosome full of bacteria they meet and look you know it just kind of becomes one big vesicle now what have you done you've mixed enzymes with bacteria so that's called the fago lysosome right fago lysosome because it's the fagos plus the lome fome that breaks down the bacteria and then what do you do exocytosis of all the debris right you release the debris okay these are what your white blood cells are doing all the time your white blood cells are undergoing these steps of Phagocytosis and again what are the white blood cells recognizing they're recognizing pamps on the surface of bacteria and other germs are these common patterns these common molecules that are recognized by the white blood cells they're called pamps or pathogen Associated molecular patterns examples of pamps are peptidoglycan peptidoglycan is a pamp it's recognized by your white blood cells lipopolysaccharide LPS right that's recognized by these uh white blood cells doubl stranded RNA from viruses that's recognized by your fagos or or fyes and remember who recognizes this or or what part of the foso uh or I should say fosite what part of the fosite recognizes the pamps it's that receptor the pattern recognition receptor right the receptor recognizes the pattern there's a binding and then a phagocytosis okay these are those receptors the pattern recognition receptors these are the receptors on the surface of your white blood cells on the fago sites these PRS these receptors recognize patterns or pamps they're responsible for binding to the pathogen and then triggering ing phagocytosis okay we're going to skip toll like receptors let's skip this one I told you what the fago lysosome does when the F fagos and the lome fuse there's digestion that destroys the ingested material death occurs within 30 minutes the bacteria is digested and destroyed within 30 minutes of Getting phagocytosed By a white blood cell we can skip uh this slide here let's skip this slide here okay now let's talk about inflammation with inflammation when when you have inflammation this is a common reaction to any kind of traumatic event in the tissues tissue damage itself tissue damage itself can trigger an inflammation inflammatory response and these are the signs and symptoms of inflammatory response uh of an in inflammation ruber callor tumor doar and loss of function these are the signs and symptoms of inflammation so let's talk about what these terms mean ruber refers to redness redness caused by increased blood flow to the area increased circulation remember vasodilation occurs during inflammation so more red blood cells more blood cells get to that site right and that becom comes red calor calor refers to warmth when you have inflammation it becomes warm and that makes sense because you have increased blood flow more blood is warm more blood going to that tissue makes that tissue feel warmer than usual tumor tumor refers to swelling swelling due to more fluid flow to that area and even fluid escaping into the tissues fluid what fluid does fluid leaves the blood vessels and enters the actual tissues the interstitial uh areas around the tissues and then there's doar doar refers to pain pain caused by stimulation of nerve endings and tissue damage so you see these are the four common signs and symptoms but then there's a less common one called loss of function so if the swelling and the inflammation become bad enough you can lose function like you're like you see this this person's foot is becoming so inflamed that after a while it may not be able to bend their toes correctly or walk correctly you can lose some function due to that drastic inflammation and again all the signs and symptoms of inflammation suggests that injury has taken place tissue damage alone is sufficient to trigger inflammation however chronic inflammation this is usually due to an autoimmune disease if you have chronic inflammation if you have like just inflammation that lingers for long long periods of time it's usually not due to tissue damage but some kind of uh autoimmune disease or some kind of longlasting chronic disease not necessarily damage okay and why does inflammation occur why does your body undergo inflammation well to mobilize and attract immune components to a site of injury remember when you have inflammation your blood vessels dilate and to get more for example neutrophils to do chemotaxis and move to the site of infection to set in motion mechanisms to repair tissue damage so platelets and such get to the S side of the damage in case there's bleeding right other cells get in there to repair the tissue damage and to destroy microbes and block the further invasion right pus formation clotting um all this stuff occurs coagulation clotting all this stuff occurs to prevent any more Intruders from getting in I had mentioned that inflammation is a response to tissue injury and it has different functions the functions of inflammation are to are to mobilize and attract immune components these are immune system cells to the sight of the injury to set in motion mechanisms to repair that that tissue clear away harmful substances and then also to destroy microbes and block further Invasion this is why inflammation occurs here you can see the major events in inflammation so remember what I said earlier inflammation is caused by tissue injury right so here you can see a splinter or a nail that's penetrated into the skin that causes tissue damage and that triggers inflammation okay even if this was a sterile needle that would still trigger inflammation because there's tissue damage now what happens when there's injury so there's injury then there are what's called vascular reactions this means that the the damaged tissue signals to the mass cells do you guys remember the mass cells what do the mass cells release histamine so tissue injury signals to the mast cells to release histamine what does histamine do with the blood vessels di Dil no it dilates the blood vessels right so it's called vasodilation vasodilation that promotes more blood flow to the site of the injury okay and not only not only just red blood cells but your fosic white blood cells such as neutrophils the neutrophils come to the sight of the injury as well and you you see what's happening here the white blood cells can actually squeeze they squeeze through the blood vessel and come out of the blood vessels to get to the sight of the injury why do you think the white BL why do you think the neutrophils squeeze through the capillaries to get to the sight of the damage why do you think that is to kill any bacteria yeah to to to get to where the tissue because where the tissue damage is there's likely to be some bacteria and stuff right so the white blood cells the neutrophils will literally leave the blood vessel come to the sight of the tissue damage and start phagocytosis start eating up the bacteria and other um you know any other pamps right pathogen Associated molecular patterns it will gobble those things up right and then what then after this big battle between the neutrophils and the bacteria this is pus formation right pus forms if you ever had a a healing wound or something or in infection there's pus that forms a lot of that pus is made up of macro uh uh neutrophils dead bacterium dead neutrophils right that's makes up pus and then after that there's a scar that forms and there's healing that occurs macrofagos you know mop up any lingering bacterium and there's a resolution so the the wound is healed and this is known as acute inflammatory response acute inflammatory response okay so here it is in a little more detail here look at this again this is happening during inflammation remember the tissue was damaged that released uh signals to the mast cells the mass cells release histamine histamine causes the blood vessel this is a blood vessel to dilate vasil dilation the vasil dilation actually opens up pores in the endothelial cell uh the endothelial wall as well endothelial meaning uh blood vessel you see pores open up these pores allow fluid to leave the blood vessel and as well as white blood cells such as the nutrifil and the nutrifil kind of like an amoeba you know it can change its shape and literally squeeze through the blood vessel leaving the blood vessel to get to the sight of the injury isn't that neat so margination is the term for when these neutrophils attach to this blood vessel right here you see how they attach to the blood vessel wall diapedesis also known as extravasation this is where the white blood cell squeezes through the cell uh through the uh between the cells out of the capillary okay margination neutrophils line up along that endothelium diapedesis or extravasation they squeeze through to get to the sight of the injury to to phagocytose those Invaders and by the way what's driving these white blood cells to get to the site of the infection these are called chemotactic factors remember chemotactic factors they drive Chia um not chem osmosis but directed cell movement right chemotaxis you guys remember chemotaxis directed cell movement well the tissue injury releases chemotactic factors which cause the white blood cells to go to that site they they do taxes towards that site of tissue injury and again the neutrophils the reason they're trying to get to that site of the tissue injury is to actively phagocytose and destroy bacteria uh dead tissue and particulate matter and this forms pus this forms pus pus is a whitish mass of cells liquefied cellular debris and bacteria this is a sign that there was a you know some kind of infection and a response to that infection okay um we're not going to talk about long lived inflammation skip that now fever is an adjunct to inflammation when you have inflammation specifically when you get an infection This Is Us usually accompanied by fever right so fever is when your body's temperature your body's core temperature is elevated right um normal body temperature is 37 degrees C right or how many Fahrenheit who knows 100 no 98.7 is yeah 98.7 Fahrenheit 37° uh C right so when you have a fever this is abnormally elevated above that right so a low grade fever you went from 37 Dees C to 38 this is about 100 to 101 Fahrenheit this is known as lowgrade fever now moderate fever this would be 38 to 39 1023 3° F and then high grade fever this is where we hit 40° C 105 average F okay now again fever is it accompanies infection when you have an infection this triggers a fever in your body and why why does your body enter fever State well it's interesting you're your own body triggers fever your your body wants to raise the temperature of your you know your core and this is done by releasing signals called pyogens pyogens pyro means fire and pyogens are signals like cyto kindes that trigger elevated temperature body temperature okay now your own monocytes remember I told you about your white blood cells the monocytes the neutrophils macrofagos during the process of Phagocytosis they can release pyrogens such as interlan one or tumor necrosis Factor they release pyrogens so imagine that the maccrage is chewing up the maccrage is chewing up it's it's phagocytosing foreign debris foreign bacterium this is causing it to release pyrogen and do you know what that pyrogen does the pyrogen is a signal that travels up to your brain and what part of the brain do you think it signals to who knows this hypothalamus yeah very good the hypothalamus exactly right those pyrogen signals released by your macrofagos and other fosic cells come up to the hypothalamus of the brain the hypothalamus of the brain you can think of it as a control center like the therat of your brain and your hypothalamus it responds by raising the thermostat raising the temperature higher than 37° C 98 Dees F okay and there are some benefits to this you might be wondering wait what why would my own body trigger fever that must mean there must be some benefit to Fever if my own body triggers the fever that must mean there's a benefit to fever and that's true here are the benefits of fever fever inhibits multiplication of temperature sensitive microorganisms remember many organisms you know they you know misop files they grow best at 37 degrees C this is why we incubate so many different substances at 37° C right but if your B if you put those same bacteria at 40° C what would happen they would grow slower they would grow slower does that make sense so you actually slow them down by raising the body's temperature isn't that neat so because it's outside of that optimal range it's it's not the optimal Cardinal growth temperature it also impedes the nutrition of bacteria by reducing the availability of iron bacteria need to get iron as a co-actor to grow okay iron is an important nutrient does that make sense and when you have a fever this causes what's called hypo Foria hypo Fair iron emia means in the blood low iron in the blood hypoy Remia when you have a fever your body your your blood has less available iron for a bacteria that means the bacteria have to grow slower so not only is it too hot for them to grow at their optimal rate but they also can't get the iron they need as a nutrient to grow at that optimal rate as well so it like doubly slows them down right does that make sense and then what else it also increases metabolism and stimulates the immune reactions and naturally protective physiological processes so it speeds up hematopoesis what does hematopoesis mean formation of more blood cells actually hematop pois is not just making more red blood cells it's making more blood cells white blood cells red blood cells platelets everything right so now your body is making more blood that means more more uh immune cells to fight the infection it also speeds up phagocytosis gobbling up of bad guys and other adaptive immune reactions it also increases the ability of specific lymphocytes lymphocytes are be cells tea cells natural killer cells to home in on the sites of infection okay so you see the benefits of fever your own body wants to have a fever when you have an infection right your own body triggered that fever because of the benefits that The Fever you know has so because of this for treatment of fever it's difficult to determine whether to suppress the fever or not you know more and more clinicians are they debate should we let the fever ride out or should we try to suppress the fever because now we know more and more about the benefits of fever does that make sense when I was a little kid they didn't know this so well so anytime a kid had a fever they would try to put like cold press on their head and you know like try to cool their body down and they thought it was really terrible thing to have a fever you know what I mean nowadays they're realizing oh wait there's actually a reason why there's a fever and we should just let it play out unless what unless it gets out of hand you know with the highgrade fever I was saying above 104 at that point it's like oh my gosh that high grade that super high temperature is going to do more damage to the body than you know its benefit does that make sense so usually nowadays if it's a low grade fever it's okay just let it play out you know no we don't need to try to control the fever but if it becomes a high-grade fever it's like okay we need to start taking some measures to cool down the body and uh counteract the fever okay all right moving on to one of your other parts of your innate immune system this is really neat this is known as your interferon response and it's a it's a innate re response to a viral infection it's your body's natural response to a viral infection okay so let me show you how it works so let's break this down step by step look here this is a cell in your body so this is one of your cells and look what's happened to your poor cell it has become infected with a virus right so the your cells are infected with virus and remember this is not good because the cell becomes a virus Factory there's synthesis assembly and release of virus that occurs right we all know that damage the cells and and cause infection and disease right but what's cool is your cells have what's known as the interferon pathway uh and this starts with the interferon Gene it's a gene that you have called the interferon Gene and this Gene can be turned on if the cell realizes through signaling if the cell realizes it's infected it can turn on this Gene right so this Gene is normally off but it can be turned on if the cell is infected with a virus okay what does this cell what does this Gene do this Gene product is a protein that's not just any protein it's a cyto kind it's a signaling protein it's a signal the protein is a signal what do signals do don't they leave the cell to signal to some other cell right so you see these Green Dots this is the interferon protein from the interferon Gene does that make sense and and the interferon protein is a cell signal that cell signal does what it leaves this cell and look where it's where's it going it's going to a nearby cell you see this the interferon left the infected cell and the interferon binds to special interferon receptors right on the next door cell on the neighboring cell okay so what's happened this cell The receptors activate right and it sends a signal into its nucleus you see this uh interferon receptor binding signals to this nucleus that there's a problem and what is the problem problem the problem is there's a virus coming right so what we need to do is we need to turn on genes that are going to fight the virus right does that make sense antiviral genes they're called anti- anti viral genes we need to turn on antiviral genes so we can make antiviral proteins and guess what antiviral proteins do if this virus comes and I'm prepared look look what happens my antiviral proteins can do what block the viral replication probably by chewing up its nucleic acid you know its genome degrade the nucleic acid you see so isn't that great so now the neighboring cell is immune to that virus now let me ask you this I might because I might ask you this on the exam does this prevent this cell from being infected no no it still gets infected but it prevents it from being taken over right does that make sense so that the the adjacent cell it's prepared it still gets the virus you know taken up the virus still gets in but the virus can't do any of the it can do absorption and entry and uncoding right but it can't do synthesis assembly and release does that make sense and so you've basically stopped the replication right there right you you've or the the the spread right there isn't that neat if it's bacteria that won't trigger the interferon response the interferon response the interferon pathway is specific to viral infections yeah yeah good question so this is part of your innate immune response this means that it doesn't have a memory right so these cells they're not going to remember and fight that virus better next time it's going to activate the same same way next time as it did this time there's no memory that forms there's no antibodies that form there's no nothing like that right so that's why it's part of your innate immune response okay this is an interesting little uh note from the book which I just want to share with you uh about covid right SARS CO2 the virus that causes covid see what your textbook says about anti or the antiviral interferon response to covid and how that could play a role interferon deficiency this means that you you know your body's not doing the interferon response properly right does that make sense the thing I just showed you interferon deficiency could cause some people to become much sicker when they are infected with SAR cov2 right the virus that causes covid and that makes sense because if that virus gets into your cells let's say you breathe it it's in your upper respiratory tract it starts infecting these cells well guess what if those cells have a robust interferon response they can signal to the next you know throat cell or upper respiratory cell hey don't let yourself get taken over and then what does that do it limits the spread of that infection right it it makes it so that you fight it off much faster and easier with much less symptoms and signs right does that make sense but if your interferon pathway is compromised right or deficient then what then you know it can spread and spread and spread right does that make sense and it could be much worse uh outcomes to to that uh covid infection okay all right there are also proteins in your body there are proteins that are called serum proteins uh these are known as complement proteins and these proteins actually play an active role in your immune system it's pretty interesting because when you think of your immune system what do you think of you think of white blood cells you think of macrofagos B cells te- cells but most people don't know that there are proteins that are playing a role in the immune system as well these proteins are called your complement proteins they are floating around in your blood there's over 50 different proteins in your blood that are part of the complement pathway complement proteins they work together when when these complement proteins become activated they work together to destroy bacteria and certain viruses they can actually play an active role in the immune response okay so but first there has to be an activation you have to activate these complement proteins there are three ways that complement proteins become activated the classical complement pathway the lectin pathway and the alternative pathway these are the three ways that your complement proteins become activated but I'm not going to ask you this on an exam because we we don't need to go into that amount of detail about these proteins but what do they do once they become activated these proteins become activated in your blood what can they do let's talk about that so regardless of if the activation is caused by classical lectin or alternative pathway they can do certain things they can help during inflammation they can help with phagocytosis they can help help destroy microbes destroy bacteria by forming something known as the membrane attack complex these little proteins you know what they can do these little proteins can insert themselves into the membrane of bacteria forming a hole in the membrane of the bacteria that's known as the membrane attack complex because it attacks the membrane of the bacteria this is causes the bacteria to basically lice the bacteria to basically break apart okay so again they play a role in inflammation like for example they can they can play a role in chemotaxis they can play a role in phagocytosis so they can help your fosic white blood cells to identify a Target and they can also embed themselves in the membrane of bacteria causing the bacteria to lice neat so these complement proteins are playing an active role in your immune response right okay okay and we're going to skip the antimicrobial peptides m that's the end of the chapter but I want to share with you one more thing that's not in here um it's not in let me see here yeah it's not in this packet but it's in my videos I I had you watch did any of you happen to watch them yet those five videos yep there's another one that I want to talk about but it's not I don't know why they don't mention it here it's called the natural killer cells natural killer cells these are white blood cells that are one of your lymphocytes you know your lymphocytes there's three lymphocytes there's the B cells the t- cells and the natur natural killer cells okay now what I need you to know is that the natural killer cells are actually part of your innate immune system the innate immune system so so they should talk about it in this chap I'm not sure why it's not in this chapter's packet but this is what natural killer cells do they don't have a memory obviously because they're part of the innate or non-specific immune system they don't have a memory they don't improve with each exposure right but they do play a role in your immune response so here's how they do it right so if you have a cell this is one of your cells right this is one of your cell it's a nucleated cell right so here's the nucleus of your cell your nucleated cells have a structure on the surface this is called MH C1 right all of your nucleated cells have proteins on the surface called mhc1 proteins fair enough so if skin cells liver cells heart cells brain cells they all have mhc1 proteins on their surface and the job of the natural killer cell is simple its only job is to go and this natural killer cell just checks to see does this cell have mhc1 or not right that's all it does it checks this cell okay this cell has mhc1 it goes to the next cell this cell has mhc1 it goes to the next cell right that's it that's his whole job but here's the thing why would one of your cells not have mhc1 on the surface if it's sick if it's infected or sick or something is wrong right your cells are programmed your cells are programmed to bring their mhc1 inside if the cell gets sick and what do I mean by sick infected with virus infected with bacteria um even if it's becoming a cancer did you know like a a cell that's becoming what's called transformed the cell's becoming a cancer it could realize that it's becoming a cancer sometimes s and it can internalize its mhc1 right so all of these are bad right like you don't want cells that are going to become cancers you don't want cells that are infected with virus you know this is not good right so when natural killer cells sees that here's one of your cells without its mhc1 what what does it assume it assumes that cell is in distress there's something really wrong with that cell so why not do what why not kill that cell right so it kills that cell so what do natural killer cells do simply screen your cells your nucleated cells for mhc1 as long as mhc1 is present you're good if mhc1 is internalized then it assumes the worst it destroys that cell and like I said the natural killer cell is a lymphocyte but it's the only lymphocyte that's not involved in chapter 16 you know the next chapter it's not invol involved in the Adaptive or specific immune response you know why CU it all it cares about is is mhc1 there or not right it's it's not remembering things it's not getting better you know what I mean it's that's why it's part of this chapter the innate immune response right questions about that you understand and that's the topic of one of my videos I had you guys watch you know um those Immunology videos is how do natural killer cells work and this is how they work it's very straightforward hope y all right questions about that all right and that's pretty much the end of this chapter so let's take a little break and then we'll come back for the Final Chapter right awesome let's do that