 Look, it's a naive T cell this time. Oh, geez. Okay, it looks like it's going to work. So we're starting in the same spot. And this is a T cell that is going to give rise to the helper T cell that came over and activated our B cells, okay? So it's not activated yet. The naive T cells don't bind their antigen yet. They have to be shown an antigen from a presenter who has the antigen and is presenting on MHC2. So we're not going to be able to get activated. And this naive T cell doesn't even know that there's anything going on until an antigen presenter comes in. I don't know what colors I used in the last one, but I'm going to make this cell be my antigen presenter. And it's specifically dendritic cells that do this job. Now, I told you dendritic cells were carrying out this task. What must they have if they want to carry out this task? They have to have an MHC2 platform. And guess what they have sitting on their MHC2 platform? They have the antigen in question. Now, dendritic cells, remember, they were white blood cells. They go and patrol like various places. They actually like take samples of random stuff and try to find antigens that they can then present. We learned that they also were non-specific phagocytes. So they're going to go through, they have the pattern recognition receptors. They have PRRs that recognize PAMPs. And in the act, here's a beautiful link between these two. In the act of seeing the PAMP on the invader, they also find specific antigens associated with just that invader and they take those antigens and they post them on the MHC. Then they head off to the lymph nodes, to the coffee shops, to the donut stores, where they present the antigens to a whole bunch of naive T cells that are just chilling in those zones. They say, hey, has anybody in here recognized this? If the T cell recognizes the antigen, present T cell plus antigen, nothing. T cell plus antigen on MHC2. Remember how I told you that the T cell in order to have positive selection, our T cell had to be able to bind to MHC molecules. Here's one of the reasons why. This process, if they bind, that is going to lead to activation. Once we have an activated T cell activated, that says activated, T, T cells, just like B cells, are going to differentiate. One of the things, and you already know this, one of the things that we can differentiate into is what? Helper T's and helper T's have the ability to bind to MHC2 on B lymphocytes and activate them. So helper T's are going to activate B's. Thank you very much. Activated T's can also become memories. They can become memory T's. That says memory. And memory T's are just going to serve the same function as memory, I mean memory B's. I knew exactly what I was trying to say. And activated T's, so far we've got a helper T. That's a valuable thing to activate the moral immune response. Memory T's, we're going to keep track of everything, but we don't really have anybody who's doing anything until we activate our killer T's, our killer or cytotoxic T cells. Now, don't you want to know what these guys do? Well, let me tell you, let me give it to you straight. They go out and they find, this is how these guys function. They go out and find Joe the cell. Poor Joe, I'm not feeling good about this. Joe is like, dude, you guys got to see this thing that I found in my cell. It's like this weird green thing. And I ate it. And now I want to take a picture of it and show it to y'all, because I'm not sure why I ate that thing. Killer T comes along, sees its antigen on an MHC1 platform. Killer T binds to the antigen and the MHC1 platform. I mean, it's like you have to have two layers of permissions before you can carry out a killer T task, and guess what it does? It initiates apoptosis, apoptosis. Sad story. I'm sorry, Joe. That thing that you ate, that ain't good, man. That ain't good. And we got to protect everybody else in this mug so you are going down. And Joe will commit apoptosis just like previous apoptotic processes that we talked about with granzymes and perforin. And Joe will be done. Nicely protected. There was a word that I forgot to tell you guys last time. Blurb, blob, blurf. Some, I mean, it's like, it's a fantastic word. Like we got to, I got to go look it up because how can I forget this word? The word that, bleb, it's a bleb. What? That's a real word. That's not a windy word. Doesn't that sound like a windy word? Blebbing. So if you go through apoptosis, at least that's cool. At least you get to bleb in your final hours. You like bubble off these bubbles of cytoplasm that are like, it's like backward xyto, xos, whatever. Nobody knows what I'm trying to say except blebbing is so freaking cool that you barf off things that are in little blobs that get protected. You know that blebbing is going to be my new word. Who thought of that word? I got to learn more about the blebbing phenomenon. Okay. I do agree that these two processes are absolutely connected to each other. Like we can't really separate them out. Especially thanks to this little guy down here, the helper T cell, that one literally connects the two. One thing that I want to make sure is clear in this is that both of these processes are responding to the same antigen. So simultaneously as soon as people start being exposed, as soon as people start finding the antigen and sharing the wealth, have you guys seen this thing? What do you think of this thing? Is this thing a bad idea? As soon as that all starts happening, we're going to initiate the response both sides of the response simultaneously. All right, let's look at the whole picture. Let's see, let's look at similarities and differences in the whole thing. So here's what you're going to do. And I'm going to do it too. I'm not going to do it in front of you. I'm going to combine these two visuals. I'm going to combine this one, the cell mediated response, with this one, the humoral immune response. I'm going to use similar colors and then I'm going to do like a side-by-side thing. So you can really see them compared to each other. And then we're almost done.