Biology: Antibody Mechanisms

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So, how do antibodies destroy cells? And the answer is, they don't. Basically, all antibodies do is they act as general flags that, "Foreign substance present here guys, bring in the big artillery." So, it's literally a way to mark a cell, to mark an intruder, to mark a chemical so that your big guns, your macrophages and your complement system can get in there and start, "Boom", knocking these guys around. You know there are - some day I want you guys to sit down and take a good immunology course. And learn, you know, the five different forms of antibodies and what they do and antibodies generally are referred to as Ig, immunoglobulins. IgA and IgM, and I'll tell you, there's books this thick written just about immunology and it's an incredible field and a field that there's still a lot for you folks to discover in. But let's discover a few things right here. How do antibodies work?
Well, one of the things antibodies can do is neutralization, and another thing they can do, which kind of goes along with neutralization, is called opsonization. Did you ever see the movie Fantastic Voyage? In that movie, Raquel Welch was opsonized. And what that means is that she - well let me show you what it means. What happens with opsonization is something like this. If you get an antigen or you get a large molecule and it's in the blood, it can be attacked by antibodies. And once it's been attacked by antibodies, what can happen to that thing is it can get eaten up. So, once you get, say for example, something that has been neutralized as in an antigen, or covered, as in opsonized, then it can be attacked by white blood cells. And whenever I think of this, and I teach my students about opsonization, I think of Raquel Welch. Because there was a scene in the movie where - Fantastic Voyage was a great little movie back in the sixties, I guess - and there was this thing where they had this submarine going through this human body to cure this guy's brain tumor and there was, of course, a bad guy on the submarine, and it was not Raquel Welch. She was one of the scientists and what happened was, she was out scuba diving in this system somewhere. I think they were like stuck in the neurons or something and all of a sudden she starts to get covered by these antibodies, and they got all nervous, so all the divers are around her and rescued her and you know, as little twelve year old kids, we thought it was just so funny as were like, ripping antibodies off of Raquel's body and they were stuck to her. But they saved her from the macrophages. And that was the good news. And Raquel, if you're watching, I thought you were great in that movie.
Anyway, there's another thing that can happen. There's agglutination. Agglutination is another thing that can happen. I don't have any good Raquel Welch stories for agglutination, I'm sorry. But what can happen in agglutination is kind of a cool thing. You know, one of the things that we need to talk about is the fact that a lot of these things like - well, we can use this picture again. This actually shows a kind of an agglutination. And what's happening here is you're forming a mass, and again, in forming a mass, the thing forms a large particle that will be engulfed by macrophages. You know, this is more of a physical thing. With say, neutralization, you could even do a chemical thing. You know with neutralization, to go back to that, imagine a virus. And imagine that a virus has a portion that's going to land on a cell. Remember how viruses work? I'm back in neutralization here. You could even neutralize a virus by actually causing it to not being able to land, so it doesn't have to be always a physical thing. It can be a chemical thing, too. Now in this particular agglutination example here, we're literally agglutinizing things. We used to do a lab back in the pre-HIV days, where we would do blood types. In high school and college labs and everybody would add - the way you do a blood type, is you add antibodies to it. And what we would do to show you a cool agglutination reaction, what you would do is you would take somebody's blood and we don't know what's on their blood cell, but let's just say it's antigen A. And remember about blood types, what causes things to have certain blood types. What causes things to have certain blood types are these little, literally carbohydrates. They're glycolipids that stick out of the red blood cell, and we name then A and B. So, we would take, you know you'd prick your finger and you'd put it on a slide, and to that you would add anti-inflammatory-A antibody. And you'd hit that and what would happen is you would have an agglutination reaction. If you imagine that each of these green circles are red blood cells, what we're doing is agglutinizing that, forming a clump. Now if this were not on a slide, white blood cells would come over and eat it. That would be pretty cool. There's the white blood cells coming over to eat it.
Another thing that can happen is some of these white blood cells, some of these antibodies are like this particular one is pentamerous. And this particular pentamerous one, this is IgM. We're seeing an agglutinization reaction here, look at that. Now in this one, it's working a little bit differently. In this particular one, we're literally pulling the bacteria out almost, I would guess we could call this almost like a precipitation kind of thing. You're causing all of the bacteria to come in together, forming again, a clump. Why? So your white blood cells can come over and eat it. So this particular one, this is immunoglobulin M, with its pentamerous shape, can actually - five arms - and maybe even more, remembering that each one of these things might have two active sites on it or two variable regions on it, so we're talking some heavy duty - and what's the goal here? Pulling things together, either neutralizing, either precipitating, either agglutinating, so that white blood cells can come over and munch them.
Now, don't forget there was another thing that I wanted to tell you about. And I've mentioned this before, with not too much specificity because it's a very complex series of reactions, and that is this whole idea of complement. And remember what complement is? Complement is a - 20 proteins floating through your bloodstream that are all going to act together in a very complex way, because you don't want these things rupturing your cells. But, what happens if complement is triggered by an antibody reaction - so along come a couple of antibodies, freely floating through - you know these are being produced by plasma cells - and they land. They will activate the complement system and this is particularly useful in bursting big cells. So, look at this thing. This is one big `ol foreign cell. This is its membrane. And say, you know you're being attacked by some of kind of like, parasitic amoeba, or something like that, well what complement is going to do is these 20 proteins are going to start this cascade of reactions and they're going to form, they're going to penetrate the plasma membrane of the invader, and cause it to explode. You'll have ion influxes, you'll have water influxes, and it'll cause literally a bursting of the cell.
And part of me hates to be so sketchy, but part of me realizes that immunology is something that is just a huge door to open up. But, what's most important in the context of this discussion is this. What do antibodies do? Antibodies are there to attach, number one. And number two, once they attach, they call things in. Now, remember what we said about the immune system. You know, every time, even think of this with antibodies, what are the four attributes you want of an immune system? You want self versus non-self. Are we recognizing self versus non-self here? You betcha. Every one of these antibodies are specific to certain invader types of antigens and yet they are diverse enough to handle any antigen and remember those cells that are memory cells. Antibodies are produced by B cells and B cells come in both forms, active and memory cells. So there it is you guys. The immune system and antibodies, it'll always work for you if you just give it a chance.
Animal Systems and Homeostasis
The Immune System Continued
Antibody Mechanisms Page [2 of 2]