5) Avoiding Antibodies

in this video we're going to begin discussing how some bacteria have evolved mechanisms to avoid antibodies. And so recall from some of our previous lesson videos that during adaptive immunity antibodies are going to be produced by plasma cells. And those antibodies will go on to tag pathogens and toxins for destruction by other immune cells. Now there are several mechanisms that bacteria have evolved over time to avoid being bound by antibodies and moving forward. In our course we're going to talk about some of those mechanisms and more detail. But for now if we take a look at our image down below notice that it is a map of our lesson of the mechanisms of avoiding antibodies that some bacteria use. And so some bacteria use I. G. A. Proteus is to avoid antibodies. Others use a process called anti genic variation which we'll talk more about moving forward and others yet use another process of mimicking the host cell or mimic host cells. And so we'll get to talk more details about each of these three mechanisms. Using I. G. A. Proteus is anti genic variation and mimicking host cells as we move forward in our course. But for now this here concludes our brief introduction to the fact that some bacteria are able to avoid antibodies and evade the immune system in that way. So we'll learn more moving forward. And I'll see you all in our next video

in this video we're going to briefly discuss how some bacteria are able to avoid antibodies by producing I. G. A. Proteus is. And so first we need to recall from some of our previous lesson videos that I. G. A. A. Or immunoglobulin A. Is one of the five major classes of antibodies. And so recall that the I. G. A. Antibodies are primarily found in mucus membranes and other areas where mucus is secreted for protection. And so recall that mucus membranes serve as a protective barrier and are associated with local antibodies that tag pathogens for destruction. Now once again some bacteria are capable of producing I. G. A. Protea. Aces. Now Prodi aces are enzymes that are going to degrade other proteins. And so I G. A. Proteus is our enzymes that specifically degrade I. G. A. Antibodies found in the mucous membranes. And so by degrading the I. G. A antibodies, these bacteria are able to avoid the adaptive immune response. And so if we take a look at our image down below, we can get a better understanding of how some bacteria capable of producing. I. G. A. Proteus is are able to degrade I. G. A antibodies uh in the mucus and therefore evade the adaptive immune response. So if we take a look at this image notice that we're we have a figure of a person here and we're specifically zooming into an area uh that is going to have mucous membranes. And so zooming into this area you can see here we have uh the uh mucosal cells and we've got the mucus embedded here and notice that in the mucus we have these I. G. A. Antibodies that are there to protect us from pathogens. Now if the pathogen like this blue structure that you see here is a pathogen that produces I. G. A. Protean bases such as these little red circles. Then the I. G. A. Proteus is will degrade all of the I. G. A. Antibodies and make them nonfunctional. And so the degraded idea antibodies are not going to be able to tag these pathogens for destruction. And so these pathogens are therefore able to evade the adaptive immune response by producing I. G. A. Proteus. Is that degrade the I. G. A. Antibodies. And so this here concludes our brief lesson on how some bacteria are able to avoid antibodies by producing I. G. A. Proteus. Is. And so we'll be able to get some practice applying this as we move forward and also learn more as well. So I'll see you all in our next video

in this video, we're going to talk about how some bacteria are able to avoid antibodies by a process known as anti genic variation. And so once again in order to avoid antibodies, some bacteria are able to constantly change or constantly alter their surface antigens in a process known as anti genic variation. And so anti genic variation or changing or altering the surface antigens on the surface of a bacteria allows these bacteria to pretty much stay ahead of antibody production during the adaptive immune response. And this is because the antibodies that bind to one variation of an antigen on a pathogen will not be able to bind to a new one. And so the bacteria stays ahead of the adaptive immune system by constantly changing its surface antigens. And so if we take a look at our image down below, we can get a better understanding of anti genic variation and how some bacteria are able to avoid antibodies by again changing or altering their surface antigens. And so notice over here on the left hand side of our image, what we're showing you is a microbe here in blue. And this microbe on its surface has antigen A. Which are these little blue triangles. And what you'll notice is that over here we're showing you an immune system. Cell A. B. Cell coming and binding to antigen A. On the surface of the pathogen. And so you can see the B cell binds to the antigen A. On the microbe surface. And so of course once this B cell binds and recognizes antigen A. It's going to become activated, it will proliferate and differentiate and become a plasma cell. And that plasma cell will be releasing thousands of antibodies per second antibody A. Which is specific for antigens. However, notice that the microbe has gone and changed its surface antigens and so there are no longer antigen A. On its surface. Now the microbe has antigen B. On its surface. And so what you'll notice is that the plasma cell produces antibody eh but antibody A does not bind to the new surface antigen B. And so basically the microbe here is staying again, one step ahead of antibody production by changing its surface antigens. And so then again what might happen is another B cell might come around and bind to antigen B. And the B cell will bind um to the new antigen B. On the microbe surface. And of course that will cause it to differentiate and proliferate and form these plasma cells that are now secreted antibody B, which is again specific to an antigen B. However, what you'll notice is that the microbe has once again changed its surface antigen. Now it has antigen. See on its surface and so again the microbe is constantly changing its surface antigens to stay ahead of the adaptive immune response. And so notice here we're saying that the plasma cell produces antibody B which is specific to an antigen B. But now antibody B does not bind to the new surface antigen C. And so again the microbe is staying ahead of the adaptive immune response by changing its surface antigens. And so the microbe has gone from having antigen A. On its surface to having antigen B. On its surface to now having antigen see on its surface and it is staying ahead of the antibody production. And so this is one way that bacteria are able to avoid antibodies through anti genic variation, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

in this video, we're going to briefly talk about how some bacteria are able to avoid the immune system by cleverly mimicking host cell molecules. And so some bacteria are able to produce surface antigens that are structurally similar. two molecules found on our own host cells. And so what we need to recall from some of our previous lesson videos is that because of central and peripheral tolerance mechanisms, our immune system generally does not attack self cells or molecules that resemble self cells. And so therefore any bacteria that are found mimicking self cells are not going to be targeted by our immune cells. And so bacteria that are mimicking cell cells are able to avoid the immune system. And so if we take a look at our image down below, we can get a better understanding of this idea. And again, take a look at how some bacteria are able to avoid the immune system by once again mimicking host cell molecules. And so notice if we take a look at our left hand side over here in blue, right here, what we have is a microbe. And over here in this purplish color, what we have is a host cell and which will notice is that when we take a look at the bacterial surface antigens which are these purple circles that you see here they highly resemble the surface antigens or surface proteins of the host cell. And so this bacterial cell over here is somewhat mimicking the self cells. And so here we have a bacterial pathogen mimicking the host cell. And so because this bacterial cell is mimicking the host cell, the antibodies and the T cells are not going to be directed towards those bacterial surface antigens that are mimicking the host cell. And so this bacterial cell here is practically hiding with a costume that resembles the host cell. And so if we take a look at the right hand side of our image over here, notice that we have a host cell over here and we have another host cell over here and then in the middle we also have a host cell, right, oh wait a second. It's not actually a host. So notice that it's wearing a costume and this is actually a pathogen in disguise, mimicking the neighboring host cells by producing these molecules that are very structurally similar to host cell molecules. And so notice that it's day eight and he's saying they still don't suspect a thing. And so the pathogen is able to avoid the immune system by mimicking host cells. And so this here concludes our brief lesson on this idea and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video