The Immune System: Overview

what is the immune system what are the main parts or components divisions of the immune system and how does it actually work to keep us immune or free from sickness welcome to this short video on the overview of the immune system this particular lecture will cover four main parts firstly what is the immune system what are its main components so these will be cells molecules tissues how is it divided it and then finally how does this all work together to ultimately provide immunity which has essentially been free of sickness or illness to keep us alive every day we are being bombarded and invaded by certain micro organisms and toxins and chemicals that will be harmful for us so our we need to have a system in place that essentially protects us from these harmful invaders and this is what basically the immune system is it is a system that can identify harmful chemicals or organisms it can respond to it it will eliminate and it also has memory against it for the future so this is basically what the immune system is it's a system to protect us from becoming sick ill and essentially being free from infection which is what immunity is the components of the immune system can be broken into three components we have cells we have tissues and we have molecules that help to achieve immunity when we look at the immune system it's broken broken down into two main parts it's broken into the innate and the adaptive the innate system is suggesting that it's always there so regardless of what the toxin might be what the chemical might be but also what the microorganism might be it's going to react in the same way so this is sometimes referred to be as nonspecific it's also in the way that it responds it's very quick so it's very fast moving a fast response so this would could be in seconds two minutes two hours so it's very quick in its response to the particular an invasion that it has now there is different categories or different subsections of the innate system which I'll go to in a second but the other thing that you need to be aware of there's no memory okay so if you keep getting infected let's say by a type of bacteria it's not going to respond specific to that bacteria even though it's seen it before it's just going to be the same regardless so the response here is I need to stress is it's nonspecific so regardless of what the problem is it's going to be the same when you compare it over to here this is specific okay so if you are invaded by bacteria it will respond specifically to that bacteria or that virus or that fungi or any kind of toxin or chemical that's coming it will come in and the immune system will react specifically to it now it does have memory okay so if you do have a innovator that it's you've already fought off previously it knows it has the equipment it has the ability to respond to it much quicker now it does unlike this particular the innate system it needs to be primed for it to respond so it takes some time so if a bacteria comes in it needs to first find it it needs to create an arsenal to respond to it and so this is going to take hours days weeks so it's going to be very slow okay so in comparison to this the adaptive system is a much slower but the advantage here is we have memory and it is specific now we're going to do is we're going to focus on each one specifically and we'll see how they are further subdivided and there in in there you'll see the components for each one so let's start with the innate immune system alright so now we move specifically to the innate immune system or in a division of the immune system remember this is the nonspecific arm of the immune system now just before I move on the one thing I forgot to mention that in the introduction is that the immune system not only is important for eliminating identifying and getting rid of say microorganisms and potentially toxic chemicals but it's also has the ability to kill off cancer cells or any cells that are essentially dysfunctional so it has that ability to also do internally your own cells that are potentially problematic now with the immune system so with the innate immune system nonspecific it will react the same regardless of the type of microorganism let's just for an example we'll focus on a bacteria so the innate immune system has kind of two lines to it the first line and the second line so this is essentially preventing the bacteria to invade and get inside you okay the two parts to it are skin and the mucous membrane so if you simply look at your whole body if a bacteria tries or wants to get into you it it has to first overcome either one of these two the majority of you on the outside is skin okay so skin is its own system but it's made up of a couple of things that help prevent microorganisms getting in firstly we have the actual anatomical barrier which is the keratin so what what it really is is at the bottom layer of the epidermis is you have the live cells and they produce new cells every day and as move up towards the outside they die and they become keratin which is protein so you just have these highl packed dense layers of protein keratin which is just on top of each other which makes it really difficult for organisms to try and get through so it's that tight packing which helps prevent organisms getting into your inside your live cells but also and also it's going to prevent acids and bases and also chemicals from the bacteria eroding holes and getting inside so it has a very strong protective value also your skin releases certain chemicals like oils sweat antimicrobial chemicals to stop a lot of bacteria growing on your skin there's also hair in strategic places like your ears and your nose that also helps prevent certain possible invasion from organisms so we have the skin okay the majority of your body is skin so that's how that works moving to the mucous membrane this is basically anywhere else where there isn't skin and so this would be in your mouth and your nose in your rectum vagina urethra okay so these are the other areas where microorganisms can get in you can breathe it in you can ingest it can go through your nose or he'd go vagina all up into the urethra all the rectum so to protect you from that we have mucous membranes mucous membranes are essentially cells that produce certain chemicals that help stop the invasion of these organisms in this case the bacteria so you have mucus it's a very thick substance which bacteria get trapped in and then they thin your immune system come and your immune cells can come along and kill it we also have cilia which are little hairs in your respiratory tract which in conjunction with the mucus the bacteria or the organisms get stuck and the cilia will push the mucus with these the bacteria up into your throat which is generally then will swallow that will then send it down to your stomach and in your stomach you have gastric acid so any the majority of microorganisms would be killed off in this stomach acid in your stomach also when you ingest food which would have bacteria in it the stomach acid would kill off the vast majority of those in the vagina we have a lower pH so this is through a lactate or lactic acid and that prevents a lot of bacterial growth in that region also around say your eyes and your mouth you have saliva and tears they a watery substance with chemicals in it such as lysozyme which are enzymes and also antimicrobial chemicals also preventing the possibility of bacterial growth etc and then finally you Ryan although this is this is a waste product of the kidneys it does have a lower pH so again making it a bit harder for microorganisms to grow in bladder and urethra and also the force of the urine being flushed out through your urethra make it a lot harder for bacteria etc to grow in so these are all the first-line so they're always there happening all the time to prevent invasion however if there was an invasion that was to occur then the second line will take over remember this is still part of the innate immune system so within the second line of the immune system we have cells we have a physiology which is processes that can be turned on to help stop the infection and we have certain chemical release starting with cells these are essentially the white blood cells that are produced from bone marrow except for lymphocytes lymphocytes are part of the adaptive immune system so all the rest of the white blood cells are important for the second line of the innate the first thing we have a group of cells which I'll go through now which are called granulocytes these are made up of neutrophils sana fuels basophils and marcelles they're granulocytes means they are filled with granules that certain things that are inside their cytoplasm which they release to either notify the body that there's a problem or bring more cells into it a common one would be histamine starting with the first cell neutrophil this is the most abundant white blood cell and these are usually the first cell the first white blood cell that comes to an area of either injury or infection so they're very abundant and they're the first on the scene to notify more cells to come but also they're very good at a process called fugg phagocytosis which is eating up cells okay so they do a lot of that they're very good for that that's that's a neutrophils the next one is sana fills their name because they are stained with a acids name called Pearson now they are most important for parasites so certain parasitic infections in the world like schism it's kismet ptosis where you'd find that in South America Asia Africa asana feels would go to the point of the parasite they can't even though they are a phagocyte they can't actually eat the parasite because it's too big but they attach themselves to it produce a whole lot of chemicals like enzymes like reactive oxygen species and that will help destruct the parasite so they're very good in parasitic infections Bezos basophils also what blood cell also a granular site seems to be strongly involved with allergies so certain allergic reactions these cells be more dominant and they'll work with mouth cells particularly with some antibodies to cause reactions to try and get rid of the allergic or the allergen that is causing the problem they also have the ability to bring in the asana fuels at a later date and this is where you see the recruitment of asana fuels in things like allergic asthma finally in the in the granular sites we have the marcelles which is really important these cells are filled with histamine and so they're going to notify the body to create inflammation these are located in very strategic locations like skin mucous membrane or under the skin under the mucous membrane in blood vessels and when there is a breach of the first line these Mar cells will release histamines which are going to cause inflammation now I'll skip these guys for a second and we'll go into the physiology so inflammation we've spoke or I've done a video on it acute inflammation so if you haven't watched that please go and look at that video but inflammation is essentially a physiological response again it's nonspecific to any kind of cell injury so what it basically happens when when there are cell injuries or infected cells chemicals are release in most commonly Mar cells will release histamines and then through a whole cascade of processes we get more blood to the area more extra date to the area and more chemicals in the area which are going to make the area inflamed redhot painful but also bring more red blood cells into it so that's the inflammation the other physiological response is fever so when you are infected or have a very high inflammatory response there are certain chemicals that are released like cytokines and interleukins and they also go into the blood but they go in the blood up to the hypothalamus and tell the hypothalamus to become hotter and that heat seems to be a physiological and innate response to help get rid of certain infections particular bacterial and viral infections so that is a physiological response finally some chemicals that are released in the second line interferons and complement proteins interferons can be released from cells that have been infected by viruses so it seems that when the virus comes in hijacks your cell and tells your cell to copy itself this cell as it's doing so it will release some interferons which will go to its neighbors and kind of and notify the neighbors that we are infected with the virus please be aware of this don't allow viruses to come and hijacked you and essentially take over your machinery and start copying so these are special viral proteins that are released by infected cells from viruses that kind of prevent further cells being infected by viruses okay but again it's nonspecific because it's not specific to that type of virus it's just viruses in general complement proteins these are a whole collective of proteins that are in your blood all the time but they're inactive now when there is a inflammatory response or an infection response these proteins become activated in your blood seem to go to the site of injury or infection and all congregate together as a big group and when they're activated as a group in a cascade they seem to be able to put holes in other bacteria or cells that are injured or infected so they can essentially protect you in that way through breaking holes in cells or bacteria that are that are present so that's the chemicals but also with the chemicals just be mindful that there are a lot of chemicals mediators in inflammation like cytokines like prostaglandins like histamine that could also fit here but these are unique types of chemicals finally we go back to these few which are dendritic cells monocytes and monocytes are found in the blood which are also type of white blood cell but when they become activated in tissue they become macrophages macrophages are very important with the neutrophils for phagocytosis but the reason why I'm putting these out dendritic cells monocytes macrophages what they do different to the other white blood cells is they antigen present so when when they do their phagocytosis so they chew up break down microorganisms like viruses or bacteria they ingest them break them down but the proteins on these bacteria or viruses or microorganisms they then present it on the outside of their membrane which allow then the adaptive system to come in so now the adaptive arm of the immune system will come in to the inner sorry to the antigen presenting cells so let's say you were infected by bacteria the bacteria was then chewed up swallowed by macrophages and macrophages break it up but then present parts of the bacteria on its outside the skin outside of the cell should I say and then some cells from the adaptive system most know it'll be t-cells will come along and now you will activate the adaptive system so this is where the two merged together and have some crossover which is I'm about to go to the adaptive system but before I do the final cell just to be aware of natural killer cells so these are cells that essentially just go around the body and if they sense that either there's a cell that is infected or a cell that is dysfunctional they will kill it or essentially tell it to die which is about ptosis the way that they can do that is it seems that infected cells or dysfunctional cells lack certain identification markers on the outside called MHC or major histocompatibility complex they lack that so these natural killer cells attach tell them through a chemical process that you need to kill yourself go through apoptosis and then that happens so that's the innate immune system all the different parts are two lines and the different components which you can kind of see the components here so we've already done one division now we go the second arm of the immune system the adaptive immune system as we saw this is the specific arm there's two subsections of this there's the humoral and then there's the cell mediated the humoral arm which means in fluid was named because antibodies float around within the blood or the fluid of the body and antibodies are produced from B cells so both of these cells that are going to be involved in the adaptive system are lymphocytes so this is the other two types of cells in the white blood cells we did the whole group of granulocytes and fourth but this is one these groups are the lymphocytes so for the humeral we're talking about b-cells the reason why there could be is because they mature in the bone marrow now the b-cells are the ones that produce antibodies but at the point before they've been activated or primed by the specific type of microorganism in this case of bacteria they are what we call naive so I'll leave that for a second and we come across to the cell mediated arm the cell mediated unlike working with antibodies these work specifically with cells now these cells are the T lymphocytes or the T cells these type of lymphocytes they're called T because they mature in the thymus which is kind of in the neck there's two subcategories there are what we call the T helper and the T cytotoxic sometimes the T helper cells are called cd4 + C D stands for cell differentiation so these have a receptor on them called cd4 which is sitting on the receptor of the outside of the cell of the lymphocyte whereas the C D so it sort of toxic T cells these are cd8 meaning they have a different receptors of these guys being eight which is on the outside of these cells also like we saw over here at this point in time before they are primed they are what we call naive so how do we get the selection for in the priming of the adaptive immune system to respond to a specific infection down here I've drawn a bacteria which is a green particular cell with these red flags over the red flags there to indicate an antigen which means something and that is foreign that your immune system will react to specifically remember specific means adaptive so this but bacteria let's say has breached and gone into your finger it's overcome the two barriers of your innate immune system being is skin and so forth so it got through this bit of inflammation etc but the bacteria are replicating replicating replicating so the bacteria is starting to cause problem so we need to bring in more arsenal to come in and specifically get rid of it okay so with the bacteria the bacteria will infect your cells in your finger now that we've some cells that will get infected directly by it so some cells let's say we'll get the bacteria incorporated into it these could be phagocytes or these could just be any type of cell in your finger that could be infected now it's less likely bacteria that it's less likely bacteria to specifically invade the inside of your cell because they're more extracellular virus is a more intracellular but let's just say for this case this bacteria has gone in infected one of your cells in your finger and now it's damaged dysfunctional and possibly may die before it does so there are receptors on the outside of your cell okay all your cells have this and in this particular case this one is called the MHC one mean major histocompatibility complex one receptor so this will present a type of let's say antigen on it okay which will present on the outside it's not an antigen presenting cell but it's just a part of the antigen with the bacteria that presented on this MHC one receptor now this will present - oh this will ink come into contact with the cd8 the cytotoxic T cell okay through a a communication between these receptor what it will do is it will find the right type of cd8 cell that has a receptor that will fit into this receptor with this type of antigen so there are thousands and thousands of different type of naive cd8 cells but there's a particular one that will lock in to this type of cell with this type of antigen and now it's activated so now this cell is activate this type of city 8-cell which means that this cell is now selected for and now primed okay what it will do is it will go through clonal expansion so it will clone itself colonial colonial expansion which means it will clone itself just keep copying copying copying copying the that type of cd8 cell that is specific to that type of antigen now there would be two groups of cells that it will make I'll get a blue one one group will be a memory memory cd8 cell and one will be a cytotoxic T which just means that's the one that's going to do the killing this one will go kind of down and want to start doing more killing but we'll leave it at that point I just want you to know once it's selected four it'll go through a level of clonal expansion which is going to make two subgroups a group of memory cells which are just going to hang around in case they encounter this bacteria again in weeks two months or a group that's going to go and try and kill cells that have been infected with the bacteria so that's one part of it there's going to be also some cells that will phagocytose it so it will actually eat them up so there'll be some cells that will eat it and swallow it and you'll have the bacteria inside it like with the antigen so these this cell will start to gobble chew it up and what it'll do is will it will then through its own receptor on the outside present it so it will put the red flag on the outside to say hey we've got an antigen for a bacteria that we want to show you this particular and this is what we call an antigen presenting cell and these can be dendritic dendritic cells one of the most common they are found in the skin or it could be also macrophages and other antigen presenting cells even b-cells can do it but we'll just stick with the dendritic cell this will come and bind to a cd4 helper cell which is also naive at this point again like we saw here there are thousands of different subtypes of naive cd4 cells but there will be one that's particular for the one thing I did forget to mention this type of receptor is an MHC 2 unlike this one over here which is MHC 1 so this one with the antigen will select for a particular type of city for which then activates this one just like we saw over here now it is primed which does two things one will become a memory one will become memory cd4 just like we saw the memory city for just 438 like we saw last time this is for a later date in case we encounter the bacteria again but another group will just go through and copy itself through cloning itself again so clonal expansion which means we make heaps of CD CD 4 plus for that particular antigen and what do these cells start to make lots of cytokines and one of these cytokines do well they'll notify your other branches of the immune system to come along and do some more killing so some examples are natural killer cells some macrophages but also b-cells so these are chemicals psittacosis flooding them the finger full of cytokines like interleukins etc which will bring more natural killer cells more macrophages along which with the communication of this particular type of receptor and antigen those two types of cells can come and select for the bacteria and just start killing all that bacteria but the b-cells what it will do is it will send a chemical signal across to here to tell the b-cells at this point they're naive to select for the B cell that is specific for this antigen and again there are thousands and millions of different types of B cells on the on the surface of the B cells we have this thing called an antibody which is that black Y thing I've drawn there so there's going to be one particular type of b-cell that is specific to this red antigen and when it selects for through a communication here it will activate the B cell so now it becomes primed now what the B cell will do is two things it will also clone itself one group will become memory B cells and the other one will become plasma cells now what are the plasma cells they are basically just filled with antibodies so they are just filled with antibodies and these antibodies are selected for or specific to that type of antibody from that B cell which was selected for from this particular cd4 cell which was selected for from that bacterias antigen so that means all of these antibodies are now just specific only to that antigen and they start to get released into blood and this is essentially what the humoral part is so now your Bloods filled with these antibodies particular just for that one antigen so once it floods through your body if there's bacteria else in the body the antibody will bind to it so the antibody will bind like this like that now that this is this will do a few things when it binds to it a flash will go off like a siren which will bring on say the seed of toxic t-cells which will go and kill them and also bring other macro macrophages and other cells that can do the killing and kill those but also the other antibodies what they will do is they will stick together so all these antibodies will clustering together and their bacteria will kind of cluster in and come out of solution which will also tell the the macrophages and the neutrophils to come along and get rid of it they will also neutralize it so if the bacteria has certain harmful chemicals or toxins it will neutralize it to stop any more injury it will also activate the inflammatory response so more cytokines will be released more histamine so more inflammation more white blood cells will come to thee the site it will also activate the complement system so the complements it's in which we saw in the innate system will come along and bore holes into it and kill it and optimize it which means again it kind of clusters that up brings it out of solution and can be killed off so that is essentially the specific or the adaptive response to a particular bacteria now once this bacteria is being killed there's no more bacteria in it because we have memory cells memory memory that means when the bacteria comes along again with the same antigen maybe in a month time or a year's time your immune system is much more efficient and it's a it's a lot quicker because it has memory to it okay it doesn't have to go through all this clonal expansion which takes days to maybe even weeks to get to the point of overcoming this bacteria it's much quicker and it can get rid of it much more efficiently and this is the basis of where we do vaccines or immunizations is you get memory to it so when you actually encounter the real infection you're very efficient and you can get rid of it so hopefully what you've seen is this this particular system is specific the case that we gave was this particular BAC bacteria which has a type of antigen which activates the naive T and B cells which can do a combination of cytotoxic which is killing the infected cells directly or helping the cd4 cells helping prime the other parts of the immune system particularly the phagocytes and the B cells and the B cells primarily used in antibodies can also help with the way that the antibodies bind to the bacteria or the infection and also bring other recruitments in to get rid of the infection so hopefully what you've seen for this video is the immunes what the immune system is the different components the two arms being the innate and the adaptive and how it all works together to fight infection

Channel: Dr Matt & Dr Mike

Views: 18,379

Rating: 4.9511003 out of 5

Keywords: Immune system, immunity, adaptive immune system, innate immune system, specific immune system, non specific immune system, white blood cells

Id: UsZ_zHfFeR0

Length: 33min 57sec (2037 seconds)

Published: Sat Mar 07 2020