hi everyone and welcome to chapter 11 immunity now in this chapter we have two parts part one the immune response we talk about phagocytes and lymphocytes again and we talk about it in more detail and in part two there's immunity vaccination and autoimmunity and actually there's also a bit little bit here about antibodies now without further ado let's go into part one the immune response now before we talk about their immune response and the processes involved let's talk about some definitions immunity when we talk about immunity is really protection against diseases if i say that i have immunity against this disease this means i'm protected against these diseases the immune system however is the body's defense system there are mechanisms in place these cells in place all together defending the body against diseases now as we continue this chapter imagine it in your head like a wall now be the body are fighting a war continuously every single day against different pathogens your cells your systems they are sort of like little soldiers that are trying to protect your body against any infection and like any war there are different lines of defense in a war there's like the little soldiers that are on foot usually in the front and then the soldiers on the horses and the soldiers of the machine guns and maybe the tanks afterwards same idea our body have different lines of defense as well the first line of defense is external this includes the saliva the tears skin mucus stomach acid and these are all non-specific mechanisms which means they are not targeted towards a particular type of pathogen they are just generally for majority of the pathogens very general it acts more of like a barrier between the outside environment and the internal environment second line of defense though is internal so if the enemy pathogens make it past the first line of defense they will encounter the second line of defense which mostly involves phagocytes and are also a non-specific immune response if the pathogen survives the second line of defense the third line of defense comes in and this time it is a specific immune response and this involves lymphocytes what do we mean by specific specific means that the immune response is specially targeted at that particular few pathogens now like in a war there are many many lines of defenses there are many mechanisms but they all work together and the same idea here both non-specific and specific defenses have slightly different functions different way of working but the aim is the same they work together they have teamwork in order to protect their body against diseases now there is one word that will keep popping up as we go along as well and is this word called antigens now there are two types self and non-self you might have heard these terms in chapter four we talked about how um protein like a protein and glycolipid can act as cell surface antigens what does that mean this means they are big molecules macromolecules on the cell surface and they are they function to carry the identity of the cell okay so let's talk about this further what is non-self negligence first okay notes of antigens in bio is is defined as macromolecules that activates an immune response now this is not necessarily on a pathogen it could be on um foreign surface material service any foreign surface such as allergens does some of you are allergic to dust and allergic to different things it doesn't need to be a pathogen okay it also can be your own cells which are infected by those pathogens all these things have non-self antigens and can activate an immune response what do we mean by activate and immune response we mean that this stimulates the production of antibodies by your cells okay and this antibodies will help defend your body against these macromolecules and these cells now it's important to note that different pathogens have different antigens here some have one type per pathogen some have multiple types per pathogen here so when your cells recognize non-cell antigens your cells actually can tell especially the specific mechanisms which pathogen is coming in and what antigens are expressed on the surface now the second type here is self antigens or what we also call cell marker now these are macromolecules on the surface membranes of whole cells and these antigens do not trigger the immune system that means no antibodies are produced and there is no attack going on there note when we say antigen in general though we are always referring to a non-self antigen usually if it is self-antigen we usually will explicitly say it so don't be confused when you just say antigen in general we really mean non-self antigen yeah okay so in light of that let's define immune response again now immune response is the body's immune reaction or processes that target non-cell antigens now this involves white blood cells that are made in the bone marrow that you already know in chapter 8. there are two types okay two major types which are phagocytes which are mostly non-specific as we saw just now under phagocytes there are neutrophils and monocytes which mature into macrophages there is one type one huge group the second type is lymphocyte lymphocytes we learned that there are b lymphocytes and helium phosphates and they are mostly involved in specific defense the following sites will be a recap of chapter eight but they are overlapping the chapter and it's very very important for you to understand this chapter so we are going to go through it again but i'm not going to highlight every single thing to you uh i'm just going to highlight what is important for this chapter and important for what i'm going to say next so again there are two main types of white blood cells phagocytes and lymphocytes right phagocytes are produced throughout life their function is to petrol in tissues and blood and organs and remove dead cells and pathogens now it's called phagocytes because they are cells that undergo phagocytosis they are involved in non-specific defense and responds to many different non-self antigens this is what non-specific defense means it can respond to many different non-self adhesions not just one now there are two types of phagocytes that we learned about neutrophils monocytes which then mature into macrophages now neutrophils have uh receptor proteins to identify pathogens as non-self okay and they tend to accumulate at the site of infection however it sort of dies after digesting those pathogens they don't continue to live on they just kill and then they they're like suicide bombers okay they just kill the pathogen and in the process kill themselves now for echocytes that are monocytes and macrophages works differently now they look different they also have receptor proteins to identify pathogens as non-self but they are not short-lived they are not suicide bombers they actually start or initiate the immune response so this is a specific role of macrophage here this is not in chapter 8 this is new content so let's go so macrophages they are not like neutrophils they live longer they also engulf the pathogens but in the process it starts the immune response and does this okay so here we have a mechanism number one yes again it has many receptor proteins on the cell surface you cannot see here but i assure you it's there it can detect non-self antigens and it's non-specific as we have led now like neutrophils in general they engulf the pathogen via phagocytosis okay and in chapter four we we know that after engulfment membrane fuses and after that phagocytic vacuole is formed the phagocytic vacuole actually fuses with a lysosome the hydrolytic enzymes in there cuts up those pathogens using lysozymes yeah and that's seen here nutrient form and what happens next is very interesting number five antigen is presented on the cell surface it doesn't just destroy it and throw it away it takes it and presents these antigens on the cell surface these antigens are non-self antigens these antigens are from the pathogen it takes this antigens and presents it to other white blood cells and therefore we call this macrophage as antigen presenting cells or apc they only ex they only present some antigens though the other cell fragments are released by exocytosis um yeah and the apc's or antigen presenting cells go on and activate and stimulate lymphocytes not showing this diagram now i know we're talking about macrophages here but actually this process that we just talked about can include b cells and can include other phagocytes as well one that you won't see in our textbook you won't see in my slide but one that's in many videos is called dendritic cells dendritic d and dri t i c now that's the side model the point is macrophages they are longer live they cut the pathogen up and they present the antigens on its surface and it starts off the immune response right so it starts it off by activating and stimulating the lymphocytes about lymphocytes let's go even further let's talk about it even more so lymphocytes are produced in a bone marrow before birth they are involved in specific immune response and only responds to specific non-cell antigens if they if the receptor on the lymphocytes are not complementary that particular non-self-antigen it will not be so-called activated these lymphocytes circulate in the blood and lymph and as we know from the name lymphocytes it actually has a high concentration in lymph nodes and actually it also accumulates at the site of infection now its appearance is different from neutrophils different from macrophages just so you know now for lymphocytes there are two types of cells b lymphocytes and t lymphocytes b lymphocytes the metronome and bone marrow produce the bone marrow and merchantable america for the bees in the name b cells and they produce antibodies the second type t lymphocytes are made in the bone marrow but mature in the thymus and do not produce antibodies now this is actually a very summarized version of what actually is going on they actually have even more detail talking about lymphocytes and what they do let's see let's talk about it more in the next video