 Welcome back to our meds smarter lecture series where we're taking a smarter approach to preparing future physician Before we get started if you'll take just a quick minute and click that like button and also Subscribe and turn the bell on so that you'll be notified when we post new videos Let's continue on discussing about our lymphoid structures and discuss our natural killer cells So first and foremost the natural killer cell lymphocytes are members of the innate immune system they use perforin and Granzymes to induce apoptosis of our cells that are infected by viruses as well as our tumor cells As you can see here on the right this picture, this is a scanning electron microscope That's been colorized that just shows a picture of what our natural killer cells will look like at a very very microscopic level specifically with natural killer cells their activity is Enhanced by the IL-2 IL-12 interfere on alpha and interfere on beta cells So how do they work? Well, they activate themselves to kill when they are exposed to non-specific activation signals or to target cells and or to an absence of the Major histocompatibility complex one or MHC one on our target cell surface Natural killer cells also can kill via an antibody dependent cell mediated cytotoxicity And in this case how that works is we have CD 16 Binding to the FE region of a bound IGG that should be an IGG right there It's a bound IGG which will activate the natural killer cell Let's continue on and talk about our B cells and our T cells of our lymphoid structures B cells specifically function for Humoral immunity They will sit there and they will recognize and present the antigen that will undergo somatic hypermutatization Which will optimize antigen specificity Basically our B cells produce our antibodies so the antibodies will then differentiate into plasma cells that will can secrete Specific immunoglobulins so you can have your IGG your IgM your IgA That's where they come from from our B cells part of that humoral immune system So if you see here in this picture, so what's happening? You can see this antigen the star this blue star is the antigen it binds to a B cell receptor if It has the specificity for that particular antigen alright sometimes you can have instances where the Antigen cannot bind to the B cell because it doesn't have that antigen specificity Helper T cells can come in here and induce chemical signals from that antigen that has been bound to the B cell That will transfer it or translate it into a plasma cell Plasma cell creates the antibodies to that antigen that it's recognized and it releases the antibodies out into the system Furthermore our B cells maintain the immunologic memory. Alright, so you talk about You've seen an antigen before and your body has memory for it and is able to produce the antibodies much more quickly Because it has memory that is due to our B cells so B cells give us the Memory to persist and accelerate future response to the antigens So let's say you've been exposed to a one particular antigen which we'll call antigen a And that antigen comes up and it binds into that B cell that B cell then goes down through the help with with the help of the helper T cells and releases antibodies into our body the B cells also remember that antigen a that they come in contact with and Down the road if you come in contact with antigen a again This whole process is sped up much more quickly so that it doesn't have to produce those antibodies as slowly After recognizing that original antigen All right, let's continue on and discuss some T cells T cells here our cell mediated immunity, so we're gonna see CD4 T cells that come in and help our B cells make antibodies and produce cytokines that were recruit phagocytes and other leukocytes Our CD8 T cells here actually go in and kill virus-infected cells and tumor cells Using that same perforin and granzymes that's similar to our natural killer cells that we talked about just a few minutes ago T cells are a part of a delayed cell mediated hypersensitivity if you remember those hypersensitivities that is a type 4 hypersensitivity and It is associated with acute and chronic cellular organ rejection So if you have an organ transplant and you have the rejection that is due to our T cells Rejecting that particular organ based upon its genetic makeup. And then finally with our T cells You can always remember their major histocompatibility complex numbers based on using the rule of eight. So CD4 cells Match up with the major histocompatibility complex or MHC 2 Because 2 times 4 equals 8 and our MHC 1 matches up with our CD8 cells Because 1 times 8 is 8. So that's just a good way to remember that MHC 2 goes with CD4 MHC 1 goes with CD8 I've got a picture here that kind of shows the whole process of the T cell Mediated immunity and how it works, but I'm not gonna go through this right now If you can wait and come back at another video We will talk about this in much more detail when we discuss the T cells and their differentiation And then beyond that how they're activated if you found this material helpful for your studying Please like and consider subscribing to the channel also share this video so that more people can benefit from it like you have