In this video, we're going to begin our lesson on antigens. And so it's important to note that adaptive immunity, which includes cell mediated immunity and humoral immunity will actually generate immune responses towards foreign antigens in our bodies. Now, this term antigens is really just a broad term that refers to any molecule that reacts specifically with T cells B cells or antibodies. And the term itself, antigens is derived from antibody generator. And so you can see antigen with an antibody generator. Now, different antigens will differ in their effectiveness to elicit an immune response. And so some antigens will generate an immune response. But other antigens like for example, really, really small antigens usually are not immunogenic. And by uh saying that they are not immunogenic, we're saying that they do not cause an immune response. Now, immunogenic antigens are specific types of antigens that will cause a strong immune response. And so you can see the immunogenic is just referring to the fact that it generates an immune response. Now, this term ops is also a really important term and it is a more specific term than antigen is. And so ops are really just distinct regions of antigens that A B cell T cell receptor or antibodies can directly bind to. And so really, these ops are really specific regions that are found on antigens. And so if we take a look at our image down below, we can get a better understanding of these antigens. And so notice uh here in this image, we're showing you two different antigens, this red antigen over here and this other purple antigen over here. And if we zoom in over here on the left hand side, notice that this one over here on the left is being labeled as antigen A and the one on the right is being labeled as antigen B. Now notice that these specific regions that are on the antigens are specifically referred to as OPS. And so you can see that antigen A seems to have three distinct epitomes and antigen B also has three distinct epitomes as well. And so these epitomes are the specific regions where the BB cell receptors, T cell receptors or antibodies will directly bind to. And so if we take a look at the image on the right hand side over here, notice that we have a B cell receptor here in the middle that has its BC RS it's B cell uh receptors. And uh notice that the B cell receptors are binding specifically to the epitope on the antigen here. And so uh we can label these uh purple structures here as the uh BC RSB cell receptors. And so, uh again, this term antigens is really just a broad term that refers to any molecules that can react with these T cells, B cells or antibodies. And we'll be using this term antigens a lot as we move forward throughout our course. So it's important to know that it's a broad term. And again, ops are also going to be specific regions on the antigens. And so this here concludes our brief introduction on antigens and we'll be able to get some practice applying these concepts and learn more as we move forward. So I'll see you all in our next video.
2
Problem
Problem
Epitopes are:
A
A portion of an antibody molecule.
B
A portion of antigen recognized by antibody.
C
T cell receptors.
D
A molecule that binds to antigens.
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concept
Free Antigens vs. Presented Antigens on APCs
Video duration:
4m
Play a video:
In this video, we're going to distinguish between free antigens and presented antigens that are found on what are known as A P CS. And so, first, it's important to note that B cells only respond to what are known as free antigens. And as their name implies, free antigens are free floating in the environment. And that just means that these free antigens are antigens that are not being presented by another host cell. Now, it's also important to note that T cells, on the other hand, are only going to respond to antigens that are presented or in other words, T cells only pre respond to presented antigens and those presented antigens are going to be presented by antigen presenting cells. Now, antigen presenting cells are commonly abbreviated as A P CS for short. And these antigen presenting cells or A P CS are really just immune cells that will process and present antigens in order for T cell activation to occur, activating the T cell so that the T cell can carry out an immune response. Now, the A P CS that uh will be important for you to know throughout this course, are going to be dendritic cells, macrophages and B cells themselves can actually serve as antigen presenting cells. And so we'll get to talk more about these A P CS as we move forward in our course as well. But for now, let's take a look at our image down below to get a better understanding of the difference between free antigens and presented antigens. And so notice on the left hand side over here, what we're showing you is A B cell. And of course, we know that B cells have B cell receptors or BC RS. And so that's what these receptors are sticking out of the membrane of these B cells. Now notice that B cells only respond to free antigens. And once again, free antigens are free floating in the environment. And so notice this antigen right here is a free antigen because it is just floating around in the environment. And so uh when the free antigen uh binds to the BC R, that can potentially lead to the activation of the B cell and allow the B cell to carry out its immune functions. Now, on the right hand side over here, notice that we're showing you uh presented antigens and recall that T cells only respond to presented antigens and those presented antigens will be presented by antigen presenting cells. And so notice over here in blue, we have an antigen presenting cell, an A PC. And we're specifically showing you a dendritic cell here in this image. And so this antigen presenting cell can process an antigen and present that antigen on the surface using one of its uh molecules on its surface. And so this mo this molecule right here is an antigen, but it is a presented antigen. It is being presented by an antigen presenting cell. And the T cell over here will only be able to recognize antigens that are being presented by antigen presenting cells. And so the T cells don't respond to free antigens, they only respond to presented antigens. And again, the B cells will only respond to free antigens, not presented antigens. And so this here concludes our brief lesson on the difference between free antigens and presented antigens on A P CS. And once again, we'll be able to learn more about these concepts as we move forward in our course. And so I'll see you all in our next video.
4
Problem
Problem
Which of the following cell types are antigen-presenting cells (APCs).
1. Macrophages 2. Neutrophils 3. B cells 4. T cells 5.Plasma Cells
A
1 & 3.
B
4 & 5.
C
1, 2 & 3.
D
1 & 2.
E
3 & 4.
5
Problem
Problem
Many phagocytic immune cells such as macrophages and dendritic cells commonly engulf foreign or dangerous materials in the body. If these cells engulf antigens, the cells will present the antigens on their surface. Which immune cells will respond to these “presented” antigens and trigger an immune response if necessary?
