 Hi everybody, Dr. O. In this video we're going to talk about antibodies, their basic structure and function. We're not going to talk about the different classes of antibodies that's covered in a separate video. So here you see an antibody. This would be a single antibody like you'd see with an IgG or something. But the key thing to note here is that there are antigen binding sites so antibodies jobs are defined antigens and then we'll talk about the functions in just a moment. But specifically what we're looking at here, you'll notice on the right hand side at least in the middle, you have the constant region and the variable region. So the constant region of an antibody determines what class of antibody it is. Is it an IgG, an IgA, an IgM, an IgE, or an IgD. So that's constant. The class of antibody is not going to change. The variable region there at the top, that's going to be where antigens binds. This is what's going to determine the specificity of an antibody. This is going to be like if you have, I'm assuming like all four keys look the same. That's going to be the constant region. But the actual key they give you with the little grooves or whatnot, now they're all electronic. That's going to be the variable region. That's going to determine specifically what antigen this antibody is looking for. So the constant region with the heavy chains there, that's going to be what determines what type of antibody you are. Specifically what your target is is going to be those variable regions, the parts that change. All right. So the functions of antibodies, there are multiple functions. We'll cover them all here. You see the first one is going to be neutralization. So what some antibodies can do is they can just bind and coat the outside. Here you see a virus. You can also do the same thing with a bacteria or here you see a toxin as well. So here you see antibodies that are binding, that are coating a virus and a toxin. So much that they can't use their receptors to dock to their target where they're going to work. So this is going to be how a lot of your antiviral and toxoid vaccines work. They're going to grab these viruses, grab these toxins and coat them and neutralize them before they can do any harm. The diphtheria toxin is only going to hurt you if it reaches its target. It can't do so if it's coated with those antibodies. So that's neutralization. Next you see obscenization. We've used this term before. Anything that's going to tag something so that a macrophage, a big eater can find it and engulf it is going to be obscenization. So some antibodies, their job is to actually tag pathogens that would think about like a strobe light and say here, come and eat this target. So that's going to be obscenization. Next at the bottom of this one there's a few more but we have complement activation. Remember that antibodies activate part of your complement system which is also involved in obscenization calling in more immune cells but specifically it forms what are called membrane attack complexes as you see there forming pores in this cell which are hopefully going to cause it to not be able to control osmosis and lice and rupture. So those are like three critically important functions. We also then are going to have. So here we see what's called the glutenation and you see here the IgM antibodies, they're the best at this because they have five different sites. So a glutenation is when antibodies are going to cause cells to clump together and by doing so it's going to make them easier for their phagocytes to see and easier for them to ingest. So a big phagocytic cell, a big macrophage can come along and engulf all three of these bacteria now in one bite. So that's called the glutenation. There is what's called antibody dependent cell mediated cytotoxicity. So antibodies can also direct other cells to kill their target so that's going to be another example of what antibodies can do. So I think those are all of the key ones there. Let me go back and make sure we talked about all of those there. I guess the last thing I would say with neutralization is you can actually coat and bind some pathogens before they even get in. So that's going to be a big role of the secretory IgA or the IgA antibodies that line all mucous membranes of your body. They're going to try to capture and stop some organisms before they even cross the mucous membrane. So all right, that's the basic structure of antibodies and their myriad functions. I hope this helps. Have a wonderful day. Be blessed.