now we're going to get into when the antibody sees the antigen for the first time this is what we call antibody mediated immunity or humoral immunity because it's of the body humors of the body fluids this antibody mediated immunity is going to be governed by B cells and B cells are going to respond to antigens and they're going to make antibodies so first what happens is a primary response this is the first time that our immune system sees the antigen now this could be through natural means so getting the flu or it could be through means of artificially introduced so getting the flu vaccine this is the first time that our immune system is seeing this antigen and recognizing it as foreign so these B cells are going to respond to the antigen and they're going to start to make a lot of these antibodies so the two types of B cells that we talk about are plasma cells plasma cells will rapid fire off a bunch of antibodies and some of those B cells will differentiate into memory B cells and those memory B cells are going to help us with our long-term immunity so they can circulate around for weeks months even years so that if that antigen presents itself again our immune system is going to be able to recognize it so let's imagine our Primary Response is getting the flu vaccine in the fall so that antigen is introduced to our immune system and our immune system has a primary response so B cells are going to recognize it they're going to make a whole bunch of antibodies to fight that antigen and some of those memory B cells are going to be produced they're going to help us with the secondary response so the secondary has to do with our long-term immunity and this means that our immune system has memory they often call this the anamnestic response because it doesn't forget because of those memory B cells now the secondary response is going to be bigger and faster and we'll talk a little bit about why that is so let's imagine our primary resp response was getting that flu vaccine our secondary response is when we are actually exposed to the flu so we spent the weekend with somebody with a flu and that antigen was introduced into our system so our body is recognizing that antigen is being foreign because of those memory B cells that remember that antigen from our vaccination because we have The Binding of antigen and antibody plus we have that danger sign signal that okay something is wrong we've got a pathogen that's coming in here we need to do something we're going to turn on those B cells they're going to clone themselves like crazy and we're going to get a bigger response we're going to have more antibodies and because of those memory B cells it's going to be much faster as well so that secondary response is a bigger faster response now hopefully it's a big enough response so that we don't get sick or maybe not as sick if we hadn't had that flu vaccination before um to at least manage it on our own and not end up in the hospital so the antibody mediated immunity basically has these two steps the Primary Response and then that secondary never forgetting response which is going to be bigger and faster and if our body takes seriously hopes uh hopes to keep us healthy so what are the functions of these B cells well first off they make antibodies and I mentioned those plasma cells plasma cells can rapid fire off these antibodies so about 2,000 per second and remember these antibodies are going to recognize antigens and they are going to bind to those specific epitopes of the antigen so if you remember I said that an antigen can actually have several epitopes which means that many antibodies can actually bind to it I used to think that it was one antigen one antibody but an antigen can actually have many epitopes and that means that we would need many antibodies to actually bind to them the other thing that B cells do is that they can actually present antigens to te- cells and usually once B cells find an antigen and bind to it they can actually display that antigen on their cell surface this is almost like a storefront window and how they set up displays so if you're going window shopping and you're looking in the displays you're looking to see if maybe that store has something that you would like to buy it's the same type of thing with the B cells they're kind of saying look at what I found and so they kind of wait and pause a little bit before they start cloning themselves like crazy until they present that antigen to a te- cell now I talked about our tea cells as being kind of like the intermediaries without a healthy te- cell population we basically have no immunity so the B cells are waiting for these t- cells to inspect them and once a te- cell recognizes that antigen is being foreign it says yep that thing is bad okay start cloning yourself like crazy and te- cells are also going to come into play as well so B cells make antibodies and they're also going to activate te- cells and wait for that inspection from t- cells so let's talk about the different types of antibodies so a term that you often hear associated with antibodies is immunoglobulins now an immunologist would would definitely differentiate between an antibody and imunoglobulin I tend to use those interchangeably just so that you know some of the differences imunoglobulin are bound to be cells where antibodies will actually float and I showed you another picture of an antibod an imunoglobulin and they're a y-shaped protein we talked about that heterogeneity of those very variable regions that allow them to recognize antigens that maybe we haven't seen before so they're going to be defined by the constant regions and there are different types of antibodies or imunoglobulin so I often think of the acronym gamed so there's IGG IG IGM IG and IG D it's the very iable regions that are going to determine the binding to the antigen and remember because of that gene expression and that heterogenity we can get many many different um variable regions that will bind to different antigens some that we've never even seen on this planet before who knows what's coming at us um in the future so this is a blown up picture of an ant of an antibody right here and you can see where it is that y-shaped protein we've got the constant regions that Define what it is and then the variable regions which are going to bind to those epitopes so we'll talk about the different classes of amog globulins and again I always think of the acronym gained so the first one is IGG and this is the main immunoglobulin which is found in blood this is going to recruit bagosy and it's also going to activate complement and it can even cross the placenta and it can be found in breast milk IGG is one of the main ones that we see and that we also talk about IGA we can find small amounts in blood but it's actually going to be in large amounts in secretions and places where we have mucous membranes so remember mucus membranes are going to be the easy access for pathogens to get in our body so this is where IG is going to be because if we're going to meet a pathogen it's probably going to be in those areas so we tend to see a lot of these in the digestive system respiratory and urogenital tracts IG is rarely found in blood we see this more in body fluids and skin we're going to talk a little bit more about IG when we get into allergies it can actually bind to Bas of fils and mass cells and they can release histamine remember that histamine is a flare gun going off it's kind of like a directional flare gun calling all of those immune cells over to the scene well what can happen in allergies is when we have a massive release of histamine this could possibly cause us to go into anaphylactic shock which isn't such a good thing so too much of histamine is not necessarily a good thing so we'll talk a little bit more about IG when we get into the next chapter and allergies IGM this is what I call the mother of all antibodies it is the largest imunoglobulin it's basically five units put together and this is the first that is made by the fetus and is secreted into the blood during that Primary Response so remember that Primary Response is the first time that our immune system sees that antigen immune system starts making those antibodies and IGM is going to be those first antibodies igd is rarely secreted and uh we don't normally see it in healthy individuals so it's the Lesser known ones um the ones that we mostly talk about IGG IG IG and IGM so so here is a picture of all of the different types of antibodies I'm not going to quiz you on their structure the one that I do want to point out which is on the bottom is IGM you can see why I call this the mother of all antibodies you can see where it's got those five subunits together so this is obviously the largest imunoglobulin all right so let's take a look at the antibodies that are secreted during our primary and secondary responses so remember the Primary Response this is the first time that that antigen is seen now this could be through natural means getting the flu or it could be through artificial means getting the flu vaccine so our B cells are going to recognize that antigen B cells are going to divide they're going to clone themselves turn into those plasma cells some are going to differentiate into memory cells that are going to to be circulating around for our long-term immunity and we are going to get the release of antibodies if you take a look at the graph that is in sort of that peachy color that's our Primary Response if you take a look at the antibodies that are being secreted there's IGM and IG so these are going to be the first antibodies that are going to be secreted secondary response thanks to those me memory cells is going to be bigger and faster memory cells are going to start cloning themselves they're going to divide to form plasma cells plasma cells are going to Rapid Fire off those antibodies and we're going to get more memory cells so our secondary response is the blue graph and you can see that the total amount of at antibodies is much higher and it also Peaks a little bit before the primary response so it's actually peing about five days sooner than in the Primary Response and this is a good thing because if now we're seeing the flu in real time we want our body to remember that to prevent us from getting sick so this is why they call that secondary response the anamnestic response never forgetting it's going to be bigger and it's going to be faster and hopefully it's big enough to to keep us healthy so let's kind of go through the pathway of if we had a sneaky pathogen entering into our body where is it actually going to meet these antibodies so if you remember IG is going to be in those mucus membranes so our respiratory digestive tract urogenital tract all of those open orifices to the outside world that's where IGA is going to be and so IG da is going to attack those pathogens try to surround them try to neutralize them and keep them from getting further into our body so try to stop them in their tracks now let's say this pathogen is super sneaky and it is able to get into the tissues the next antibody that it's going to encounter is going to be IG that IG is going to release that flare gun histamine and that histamine that flare gun going off is going to be bringing in all of those immune cells as well as complement remember we saw complement those 20 different proteins in the innate immune system now if this pathogen is sneakier still and it gets into the lymphoid tissue without being recognized by a B cell then macr phases are going to engulf that pathogen and remember those lymph nodes are going to be the the conference room the meeting place where now those macroasia can present those gobbled up antigens that it's displaying on its cell surface kind of like that display window to B cells and also to t- cells as well so even if these pathogens are sneaky hopefully our immune system can recognize them along their path so the last thing that we will talk about how is it that antibodies fight off microbes so I've got some of my little drawings here and the first one is utenation utenation means clumping and so IGM can actually bind to the pathogens and allow them to all stick together it's almost like glue that's going to allow them to kind of congregate and stick together and those clumps are actually going to be easier for those fagos sites to find so you can see my fagos site that kind of looks like a Pac-Man and there's a pathogen that's um encoded with that IGM they're all clumped together and now that fosite can gobble them up opsonization is another thing that antibodies can do remember that term opsonize that means that we are going to coat that pathogen so that pathogen can be coated with the antibody fago sites are going to be able to bind to those antibodies and then gobble them up so antibodies can coat a pathogen that opsonization the other thing that they can do is that they can activate compliment so IGM and IGG mostly will bind to complement and activate that system and remember complement has to do with that inflammatory response and I mentioned that we talked about complement in the innate system we would also see it again in in our adapted or acquired immune system remember this is a whole body system and they're all working together to keep us healthy basically the other way that antibodies can fight antigens is through neutralization and this is really what I think of typically when I think of how antibodies are going to fight pathogens and antigens they can basically coat a pathogen and block their action so if you remember if bacteria combined to cells are going to be dangerous viruses are not going to be able to replicate unless they bind to a cell remember that term absorption so with that neutralization those antibodies coat the pathogen and basically keep it in a bubble so if it's trapped in this bubble and it bounces into a cell it's going to bounce right off it's not going to be able to bind this is typically what I think of when I think think of what antibodies do to to help protect us and finally the last thing is that IGM can directly lice some cell membranes so migm can bind to bacteria and lice them you punch a hole through a bacteria and it's not going to be able to live so this has to do with antibody mediated immunity which is really governed by our B cells up next we're going to talk about the second arm of the acquired immune system which is cell mediated immunity which is going to be governed by t- cells