 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. So now that we have processed T cell activation. Let's talk about how we activate B cells and undergo class switching So what happens first? Well, our T helper cell is going to be activated as the T cell Occurs and then our B cell receptor mediated endocytosis occurs Okay, so we're taking that activated T helper cell and we are activating our B cell by Presenting an antigen to it that is going to endocytose that particular antigen into the cell, okay? So step one Step two and Then we have exogenous antigen being presented on an MHC2 and recognized by the TCR of the T helper cell step three is going to be Right here in the middle. So we're taking that antigen. We're presenting it on the MHC to Our TCR on the T helper cell all right and then step four here our CD 40 receptor on the B cell Which is over here on the right and white is going to bind the CD 40 lag end on the T helper So which is the green square structure on the left? So step number four is where we have that binding of the CD 40 receptor and the CD 40 lag end between the T helper and the B cell Then on step five our T helper cells secrete cytokines that will determine the immunoglobulin class switching of beta cells So coming out of the T helper cell are these Various cytokines that are secreted that will then determine the type of immunoglobulin That the base that the B cell switches to so this is step number five and then the final step for class switching of B cells Activating the B cells undergoing class switching and affinity maturation and beginning to produce antibodies So all of this will then move forward to produce those antibodies Step six so we just talked about how our antibodies are created undergoing class switching using T helper cells B cells So let's talk about the actual structure and function of antibodies First and foremost on the right here in this picture. This is what an antibody looks like We have several different components to it. We're gonna talk about that right now. So our fab Area or location is over here on the right side. It is the two Arms of the Y if you look at this it does look like a Y The two arms of the Y are going to be our fab and this is where our variable hyper variable regions occur We have a light and a heavy chain that will come and to recognize our antigens So the light here is going to be the L's and the H is the heavy So you have two heavy chains two light chains that all compose the fab of an antibody Beyond that our FC region is the post of the Y or the long arm of the Y and that is down here it goes To the region of IgM or IgG and it fixes complements heavy chains here Contribute to both the FC and the fab regions. Okay, so your heavy chains make up that long arm as well as the Forks All right So you have two heavy chains make up the long arm and the forks It is the long ones and then your light chains is only found in the fab region Over on the outside as they interact only with the heavy chains in the fab region What does fab mean? All right, this is fragment antigen binding. Okay, so what does that tell you? That tells you that in this region up here is where the antigens are going to bind. All right So if you can remember fragment antigen binding That's where the binding occurs of the antigens that will then go with the FC region to present those particular antigens To IgM IgG and fixed complement. All right, let's look at the FC region a little bit closer here The FC region has what we know as the five C's Okay, the FC region is constant. It doesn't change. It doesn't matter. What antigen we're talking about It doesn't change. They will always be the same. It has a carboxy terminal end Okay, it binds complement. So there's your fifth C of complement binding it has carbohydrate side chains that help compose it and The FC region confers the isotype. So are we talking about IgM IgG IgD? whatever Those are the five C's associated with the FC region of the antibody 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