What are Antibodies? | Biology Review

Antibodies

Antibodies. Antibodies are also known as immunoglobulins, and they are large Y-shaped proteins produced by B-cells. Now an antibody is used by the immune system— you might have been clued-in by the immunoglobulin alternative name. It’s used by the immune system to identify and neutralize foreign objects such as viruses and bacteria, so if you inhale or ingest something that is foreign to your system, antibodies are going to kick in and try to neutralize these foreign objects.

The antibody recognizes a unique part of the foreign object called an antigen. It’s important to remember the difference between these two, since antigen and antibody are both similar to each other. The antibody is what’s part of the immune system, it is going to stop the foreign objects. The antigen is a specific part of that foreign object that we’re going to try to neutralize. Each tip of the “Y”— remember, we said an antibody is a Y-shaped protein.

Each tip of the “Y” has a paratope (and think of the structure of a lock for a paratope). Each paratope will only bind to a specific epitope (and think of it like a key). Let’s look at our structure over here. We’ve got our antibody, which is this whole Y-shaped protein, and then we’ve got all these antigens up here. There are lots of different antigens that could come into your body (and this is probably not what they look like, but it’s just to give you an example).

If we’re thinking of our antigens, and this area here is going to be our epitope (this part here that would bind). It’s supposed to be considered our key. If this is our lock here, this antigen binding site, (or the paratope) then it’s only going to fit with one key (a lock is only going to be unlocked with one key, you have to have the right key to get it to unlock). We’ve got our antibody, and each part of the “Y” is only going to bind to a specific antigen.

The paratope (this little shape on the end of our antibody) is only going to bind to one epitope, which is located on an antigen (so that one spot on your antigen is what’s going to be able to bind to the one spot on the antibody). If you don’t have the right key to go in the lock, (or the right lock to bind with the key) then nothing’s going to happen.

There are lots of antigens, and different antibodies can attach to different ones of those, but one antibody is only going to be able to bind to one antigen. If you have lots of antibodies floating around in your body, each one is going to only be able to attach to one antigen. You may have lots of them that can attach to one antigen and lots that can attach to another, but you can’t just say, “OK, well, I don’t really have this antigen in my body, I have this one, so let me plug that in there,” because it’s not going to fit. You have to think of it like a lock and key.

Once you have this antibody produced, it’s only going to be able to bind to the one antigen to neutralize it. Once the antigen and antibody bind (and remember, special epitope and paratope relationship, lock and key) it’s only going to be able to bind to one specific type of antigen. Once they bind, the foreign object is tagged for attack by another part of the immune system, or it is neutralized directly.

There are some antigens (some foreign objects) where if we block the antigen then that foreign object isn’t going to be able to do any more harm in your body, (the antibody can neutralize it directly) but there are other foreign objects that can’t be neutralized quite so easily. Instead there is something secreted by the antibody and it coats the foreign object, and then the foreign object is tagged for attack, and some other part of the immune system steps in and removes the foreign object.

Now that you’ve seen your antibody, and seen how it binds to antigens, and how it can either neutralize the foreign objects directly or alert the attack for another part of the immune system, let’s go back to the B-cells. Remember antibodies are produced by B-cells. Once a B-cell has been activated, (once there is some foreign object in your body that the B-cells know about) they say, “OK we’ve got to do something now, we’ve got to get rid of this.”

The B-cells can turn into antibody producing cells, called plasma cells, so they can produce new antibodies, (these plasma cells that the B-cells turned into) or they can be turned into memory cells that can remember an antigen and respond faster, in the case of future exposure. These B-cells can turn into plasma cells that produce more antibodies, if needed, or they turn into memory cells.

The memory cells are going to remember the last antigen they had and they’re going to be able to respond faster. Once this antibody has attached to this antigen, it’s going to remember it next time and it’s going to be able to respond faster, it won’t have to try all of these keys to figure out which one goes in the lock. It will already know which key goes in the lock, and it will be able to respond faster.

That’s why if you’ve been sick with something before, you might not get it again. Like chicken pox, once you’ve had it, you usually don’t get it again. You get a flu shot and it’s got antibodies in it, once your body learns how to attack that flu virus, (at least that particular strain of flu virus) then it will be able to attack it if it comes into your body again.

Now different strains of flu virus are going to have different antigens, so it won’t be able to attack every flu virus, only the ones that have that same antigen that your flu vaccine had in it. Antibodies are very helpful with maintaining your immune system and keeping you healthy, (or keeping any organism healthy) and the B-cells produce the antibodies, the antibodies find foreign objects, find the antigen on them and the particular epitope that it can bind to, and once they bind that foreign object is tagged for removal.

It’s either going to be attacked by another part of the immune system, or it’s going to be neutralized directly, and it won’t be able to harm anything it will eventually get transferred out of the body. You’ve got your plasma cells that are going to produce more antibodies for your body and your memory cells that are going to remember past antigens (past foreign objects) that have come into your body and know how to respond to them faster in the future.

Remember antibodies are also called immunoglobulins, and that will help you remember it’s a part of the immune system. Remember the difference between antibody and antigen, the antibody is what is fighting the foreign object. The antigen is that specific part on the foreign object that has to be bound to, to be able to attack that foreign object and get rid of it.

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by Mometrix Test Preparation | Last Updated: May 15, 2019