Introduction to Adaptive Immunity

in this video we're going to begin our introduction to adaptive immunity Now unlike innate immunity which we've covered in our previous lesson videos, adaptive immunity as its name implies includes components that adapt or change over time in order to become better suited and provide better immunity over time. And that's an idea that we'll get to talk a lot more about as we move forward in our course Now. Also unlike innate immunity where each individual component protects against a broad range of pathogens here with adaptive immunity, each individual component only protects against very specific pathogens which is also why adaptive immunity is sometimes referred to as specific immunity. And once again we'll be able to talk a lot more details about the adaptation and the specificity of the adaptive immune system as we move forward in our course. Now adaptive immunity is considered a dual system with two components. And so really there are two categories within adaptive immunity. The first major category is going to be cell mediated immunity and the second major category of adaptive immunity is Hugh Maurel immunity. Now cell mediated immunity is going to be targeting and destroying interest cellular pathogens or pathogens that are inside of a host cell using T cells and these t cells are going to be T lymphocytes. There are specific type of immune system cells that we'll get to talk a lot more about as we move forward in our course. Now these t cells they use T cell receptors or T. C. R. S for short and these T crs are membrane proteins that serve as receptors and they use them to generate an immune response. And again we'll get to talk a lot more details about the immune responses that T cells are capable of generating as we move forward in our course. Now again, the second major category of adaptive immunity is Hugh moral immunity and Hugh moral immunity is going to be targeting and destroying extra cellular pathogens or pathogens that are on the outside of the host cell. And rather than using T cells like what cell mediated immunity uses hume Orel immunity is going to use B cells and they're also going to use antibodies and once again we'll get to talk a lot more details about B cells and antibodies as we move forward in our course. Now these B cells, unlike the t cells they use B cell receptors instead of T cell receptors and these B cell receptors can be abbreviated as B C. R. S. And they use these B C. R. S to generate an immune response. And once again we'll get to talk about the different types of immune responses that B cells are capable of generating as we move forward in our course. But for now, if we take a look at our image down below, you can see the two major categories of adaptive immunity on the left hand side, what we're showing you is an image focusing on cell mediated immunity which again is going to be targeting and destroying intracellular pathogens such as for example a virus that has infected a cell and is an intracellular pathogen. And so notice that cell mediated immunity uses T cells like what we're showing you over here and these T cells contain T. C. R. S. T cell receptors and those are what these little pink molecules are on the surface, the T. C. R. S and the T. C. R. S are going to be. What allows the T cell to generate an immune response to a very specific pathogen. Now on the right hand side, what we're showing you is an image of hume Orel immunity and Hugh moral immunity once again is going to be targeting and destroying extra cellular pathogens such as for example these bacteria or microbes that are on the outside of a cell floating around in the extra cellular environment. And unlike cell mediated immunity Hugh, moral immunity is going to use B cells and antibodies. And so notice over here, on the left hand side, we're showing you a B cell and these B cells can ultimately eventually change in order to be able to release antibodies. And that's a process that we'll get to talk more about later in our course as we move forward. Now these B cells instead of containing T crs, they contain B. C. R. S. B. Cell receptors and that's what these molecules are on the surface and which will notice is that these B. C. R. S. On the surface of B cells they resemble the antibodies that they ultimately release. And so once again we'll talk about how these antibodies and B cells can generate immune responses as we move forward in our course. But for now, this year concludes our brief introduction to adaptive immunity and its two components cell mediated immunity and Hugh moral immunity. And we'll be able to get a lot more practice applying these concepts and learning a lot more about adaptive immunity as we move forward in our course. And so I'll see you all in our next video.

in this video we're going to continue to talk about adaptive immunity by introducing and differentiating primary versus secondary lymphoid organs. And so first we need to recall from some of our previous lesson videos that T. And B. Lymphocytes or T. And B cells are the primary cells involved in adaptive immunity where T cells are important for cell mediated immunity and B cells are important for Hugh moral immunity. Now the primary lymphoid organs are the specific organs within our bodies where immature T. And B. Lymphocytes develop into their naive forms and these naive T. And B. Lymphocytes are really just inactive T. And B. Lymphocytes. And so the naive T. And B. Lymphocytes are fully developed but they have not yet encountered the specific antigen that they respond to. And so they remain in their inactive forms when they are naive. However, whenever these naive T. And B. Lymphocytes are introduced to their specific antigen, the naive T. And B. Lymphocytes can become activated and the activated T. And B. Lymphocytes can go on to generate immune responses, which we'll get to talk a lot more about this process as we move forward in our course. Now these primary lymphoid organs are where the immature T. And B. Lymphocytes develop into naive forms. And the primary lymphoid organs includes the thymus which is where the T cells develop. And so you can see the T. And thymus can help remind you that this is where T cells develop and the bone marrow is also a primary lymphoid organ and the bone marrow is specifically where B cells develop. And so the B. And bone marrow can remind you of the B. And B cells Now, although T cells develop in the thymus and B cells develop in the bone marrow, it is important to note that both the T. And B. Lymphocytes are actually initially produced in the bone marrow. Together. However, the T cells will go on to migrate from the bone marrow to the famous where they will fully develop and the B cells remain in the bone marrow to fully develop. Now the secondary lymphoid organs, on the other hand are organs where the naive or inactive T. And B. Lymphocytes can become activated and the activated T. And B. Lymphocytes can then begin their immune functions, which we'll get to talk about their immune functions. And more details as we move forward in our course. Now, in other words, we can say that these secondary lymphoid organs are specific sites within our bodies where foreign molecules or foreign antigens are brought into contact with large populations of naive lymphocytes activating those naive lymphocytes so that they can begin their immune functions. Now the secondary lymphoid organs includes the lymph nodes, the spleen and tonsils. And so if we take a look at our image down below, we can further differentiate between the primary and secondary lymphoid organs and so notice that the primary lymphoid organs are going to have this number one next to them and the secondary lymphoid organs are going to have the number two next to them in this image. And so once again recall that the primary lymphoid organs includes the thymus, which is where the T cells are going to fully develop. And so notice that the thymus is the specific organ that is right above the heart as you see right here. And the primary lymphoid organs also includes the bone marrow. And the bone marrow again is where the B cells are going to fully develop. But once again, don't forget that both T. And B cells will be initially produced in the bone marrow but then the T cells migrate to the thymus to fully develop whereas the B cells remain in the bone marrow to fully develop. Now the secondary lymphoid organs once again includes tonsils, spleen as well as our lymph nodes. And so this year concludes our brief introduction to primary and secondary lymphoid organs and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video

in this video, we're going to introduce our map of the lesson on adaptive immunity which is down below right here. And so because this image does represent a map you can use it like a map to help guide you through our lesson moving forward. And so you can think of this map as a table of contents that includes the topics that we're going to cover and the order that we're going to cover them in. And so the way that this map works is that it starts over here on the left hand side and you follow the branches that are at the top first and then you go down and you explore the branches in this particular order and you make your way downwards. And so that is the order that we're going to be covering these topics. And so notice that on the far left what we have is adaptive immunity and that's because remember this is a map of the lesson on adaptive immunity. And so the very first thing that we're going to talk about moving forward after this is antigens. And we're going to talk about what they are and talk more details about them after we talk about antigens. Then again we're gonna be following the top most branches first. So we'll talk about the lymphocytes and more details specifically the T. And B. Lymphocytes or the T cells and the B cells first we're going to talk about the T cells first and there are two main types of t cells that we're going to talk about the site, a toxic t cells as well as the helper T cells. After we finished talking about the T cells. Then we'll move on to talk about the B cells and how B cells can differentiate into other types of cells called plasma cells. And these plasma cells are capable of secreted or releasing antibodies. And there are five major classes of antibodies that we're going to talk about moving forward. Including I G I G A I G M I G E and I G D. Then we'll get to talk about a process called class switching which applies to these B cells. And then we'll talk about B cell activation via T dependent antigens as well as t independent antigens. Uh Then after we talk about the T cells and B cells will move on to talk about clonal selection which applies to both T cells and B cells. And then we'll also get to talk a little bit about affinity maturation as well. Then after we finished talking about the limp oh sites and all those details, we'll move on to talk about immune responses, specifically the primary immune response and the antibodies that are involved with that and anybody concentrations that are involved with that as well as the secondary immune response. And again the concentration of antibodies that are involved with that as well. After we talked about these immune responses, the primary and secondary immune responses. Then we'll talk about tolerance, mechanisms specifically central tolerance and peripheral tolerance. And then last but not least, we'll wrap up our lesson talking about these natural killer cells or NK cells. And so really this here is our map of the lesson. And again we'll be covering these topics in the particular order that we talked about them here, and so you can reference this map as we move forward to help guide you and help you figure out where we are within the lesson. And so this year concludes our brief introduction to our map of the lesson on adaptive immunity. And I'll see you all in our next video.

in this video we're going to do a brief overview of adaptive immunity. However it's important to keep in mind that all the information that we're going to talk about in this video we're going to explain and break down in a lot more detail as we move forward in our course. And so if you're a little bit confused in this video, that's okay because again, we'll explain and break it down in a lot more detail. Moving forward. Now, taking a look at this image down below, this image is going to help us with our overview of adaptive immunity. And one thing to note is that we have these different colored boxes. Notice that this box that we have at the top right here. This box here represents our primary lymphoid organs which recall includes the famous and the bone marrow. And then the next box that we have which is down below here in green. This box represents our secondary lymphoid organs which you might recall include organs such as your tonsils and your spleen and lymph nodes. Uh those are all examples of secondary lymphoid organs. And then notice that we have the yellow that surrounds all of this and this yellow that surrounds all of this is referring to as the the surrounding tissues. Okay, just broadly defined as the surrounding tissues that are around the primary and secondary lymphoid orients. And so what you'll note what you'll need to recall from our previous lesson videos is that again, the primary lymphoid organs includes the famous and the bone marrow T cells fully developed in the thymus and B cells fully develop in the bone marrow and which will notice is that these primary lymphoid organs when they are fully developed. They start off as naive T cells and naive B cells. And recall that the naive just refers to the fact that they are inactive and that they have not yet encountered the specific antigen that they respond to. Now there are two types of T cells. There are side A toxic T cells or T. C cells and there are also helper T cells or th cells and which will notice is that the T cells regardless if they are psycho toxic or helper T cells they must become activated in order to carry out their immune responses and activation of the T cells is actually going to occur through an antigen presenting cells such as a dendritic cell And that's what's being shown here in the middle. A dendritic cell that is actually presenting antigens to the side a toxic T. Cell as well as to the helper T cell. And under the right conditions these naive T cells whether their site a toxic or helper will become activated and the activation of these t cells allows them to differentiate into either affect er cida toxic T cells or memory side a toxic T cells uh and the same goes for the helper T cells they can differentiate into effect er helper T cells or differentiate into memory helper T cells uh And the memory cells are all important for generating a secondary immune response when you are exposed to an antigen for a second time. Whereas the effect ourselves are important for generating an immune response. Uh ASAP now which you'll notice is that these effective helper T cells they play a role in helping to activate B cells. And so notice that the B cell here is starting off as a naive B cell. An inactive B cell that has not yet encountered its antigen. But when it does encounter its antigen it can essentially present that antigen to a helper T. Cell. And the helper T cell can then go on to activate the B cell. And the activated B cell once again can either differentiate into memory B cells important for a secondary immune response or the activated B cell could differentiate into plasma cells. And the plasma cells can directly secrete antibodies and the antibodies will carry out some kind of immune response. And so all of these ideas that we've talked about and mentioned here in this video. Again, we're going to explain them and break them down and a lot more detail as we move forward in our course. And again keep in mind that this was just an overview of the adaptive immune system lesson. And again we'll be able to talk more about this moving forward. So I'll see you all in our next video