How to structure antibodies

Hi there and welcome to a short Article antibody structure and function.  

       

 antibodies

So antibodies are protein basedand it's immunoglobulin. So we often use this Ig and it's kind ofa shorthand for antibodies. 

And the base structure is a Y-shaped structure onthere you have what's called variable regions and those are out on the ends.And that kind of makes sense because that's where the binding is of theepitope. 

 And then you have kind of the the base structure which are theconstant regions.  

So because we know antibodies are specific to specificantigens or specific epitopes. It's that V region, that variable region that'sgoing to be altered or not altered.  

But that's where all the differences will be. So that when the antigen comes in, it'll be specific for whatever that bindingsite is on that V region that's there. 

Okay so antibodies are just a proteinpiece. So they're secreted by B-cells and specifically by B plasma cells. 

and again the B cell system is oftenreferred to as humoral immunity because it's you know secreted in thebloodstream or the body fluids which used to be called the "humorus"So often that type of immunity is called humoral. 

And it acts in differentways, but in in really the kind of big picture on all of these is it binds tothe antigen and disables it in some way. So one of those is opsonization.

So you'll actually see I'm not going to draw all of the binding here. but ourantibody binding to the surface of this is our antigen (I'm just kind of making ageneric bacterial cell here) and it will coat it.  

And that attracts macrophages.And macrophages are going to ingest the antigen and then hopefully destroy itand then release it in fragments so through the process of phagocytosis.  

Sothat's one function. There's also neutralization. And relatedto that is the antitoxin action as well. So again same idea so it'scoating the antigen but like in this case by coating it, it's not able to bindto the host cell surface receptor. 

So for example if you were to have a virus,and it's counting on it spikes, right, to bind to a particular host cell for entrybut now it's coated with these antibodies, it can't bind anymore. Sothat's neutralization.  

And then antitoxin is also a type of neutralization it justrefers to not binding to the whole antigen but the toxin that it makesitself.  

Okay so that is a couple of activities. There's another one calledcomplement fixation, something separate.... 

so we've got one, two, three... And complement fixation actually attacks and lyses the antigen. So this would workwell on a bacterial cell for example. And then the last one is agglutination. 

And agglutination is again you have this binding that I drew over here but itwill cause the multiple or many antigens to clump together.  

So if you've got thesebacterial cells and they're all coated in antibodies, they start stickingtogether and become this huge mass that's here.

And that's gonna again disable that'sgoing to disable the antigen because if it's in this big giant clump it can'tbind to and attack your cells as well.  

So that's agglutination. But some of youare familiar with this going back to the blood type example which I've used inother videos is you can actually elicit this response by mixing different bloodtypes and you'll see the clumping of the blood type that doesn't match.  

So if it'stype B blood and it's type A blood that's putting in there you can get thatclumping. Okay so those are kind of the four actions of that a couple quickthings I wanted to mention are some of the sub classes so IgG that's the mostabundant. 

And the IgG again stands for the immunoglobulin. There's IgB, I'm sorryIgA, this is found or secreted in the mucous membranes. IgM, which is an early responder sooften this is drawn in when you look at you'll see it sometimes in inflammationdrawings because you'll see you know the the the steps of you know the chemotaxisand the stimulation of the immune system this is one of the early responders. 

Andthis is the one that has that kind of fun....I don't know if you want to call ita snowflake type surface there, so that's one of the first antibodies to respond atleast in that initial infection with inflammation. Okay and then there is IgD. IgD is found on B cells. And thenlast one one of my favorites because everybody can kind of relate to it, isIgE. Maybe you're a lucky person that can't.

but that's the antibody that'sactive in allergic response. And also parasitic worm infections as well. Soagain, you know, we've got these different types here.  

So remember the antibodies areprotein based. They do have some different subcategories but if you...to 

me..you could still sort of kind of group them together because the antibodies arebinding to the antigen and in some way preventing it, either by changing thesurface through the clumping or in the neutralization from getting the hostcell. 

Or maybe lysing the antigen directly or also attacking moremacrophages to the area so enhancing that phagocytosis process. And then thereare different subtypes that are there. 

You hear about IgG alot because that isthe most abundant and then IgE alot of times you hear about if you're readingup on anything regarding to allergies as well. 

Okay so that's just kind of a briefoverview it's a pretty complex system to kind of study and get into but justgives you some idea of the basics of how they workand some of the different types as well.

 I thank you very much please contact mewith any questions you may have. This is Corrie Andries at Central New MexicoCommunity College using CNM Glass.