Cells of the Immune System: Agranulocytes

So now that we've discussed the granule O sites in our previous lesson videos In this video, we're going to begin to discuss the A granule Oh sites which includes cells of the innate immune system. Now the a granular sites are white blood cells or Lucas sites with cytoplasmic Granules. However, unlike the granule, oh cites the cytoplasmic Granules of a granular sites are not visible under a light microscope. And because those cytoplasmic Granules are not visible under a light microscope, we refer to them as a granule oocytes. Now really, there are two main types of a granular sites that we have numbered down below. The first main type of a granular sites are going to be the mono sites and the second main type of granular sites are going to be the lymphocytes. Now, the mono sites are leuco sites or white blood cells that circulate in the blood and can further develop into either macrophages or dendritic cells. And so if we take a look at our image down below, notice that we're showing you our map of the lesson on the cells of the immune system. And so notice at the very top we have our hematopoietic stem cell and this hematopoietic stem cell can differentiate into the common myeloid progenitor cell or the common lymphoid progenitor cell and give rise to all of these other different cell types that we have down below. Now notice the ones that are in gray are the ones that we are not focusing on because we've already discussed them in our previous lesson videos And this includes the granular sites which we already talked about. So in this video we're focusing specifically on these cells over here which are once again the a granular site. So we can go ahead and label them here as the a grand new low sites. And these a granular sites again includes the mono sites which you see here and these lymphocytes which you see over here now, the mono sites as we just discussed up above in the text, the mono sites are leukocyte or white blood cells that can circulate in the blood and further develop into either macrophages or dendritic cells. And so, taking a look at the image down below notice we have the mono sites here and they can further differentiate into either macrophages or dendritic cells. And we'll get to talk more details about the mono sites. Macrophages and dendritic cells as we move forward in our course. Now, the lymphocytes once again uh include these cells that we see over here which are the natural killer cells, T cells and B cells now notice that the natural killer cells are part of innate immunity. However, the t cells and B cells are part of adaptive immunity and that's why they have that little star symbol next to their name right up here. And so what we are saying here is that the lymphocytes includes Lucas sites involved in adaptive immunity and the ones that are involved in adaptive immunity specifically referred to the t cells and B cells now, adaptive immunity is a topic that we'll get to talk a lot more about in separate videos much later in our course. And so that's something to keep in mind. And so moving forward here in our course, we're going to talk more details about these A granular sites, starting off with the motto sites, macrophages and dendritic cells, and then moving on to the lymph O sites. And so this here concludes our brief introduction to the a granular sites and I'll see you all in our next video.

in this video, we're going to begin talking about mono sites and the cells that derived from mono sites. And so taking a look at our map of the lesson down below on the left hand side over here notice that we're focusing specifically on these mono sites and the cells that are derived from them including the macrophages and the dendritic cells. And so these mono sites are capable of developing into one of two main types of fag acidic cells or cells that are capable of performing fagot psychosis or cellular eating. And so these two main types of cells are going to be the macrophages and the dendritic cells. Now the macrophages are once again fag acidic cells meaning that they're capable of performing fagot psychosis. And they also serve as sentinel cells which recall our lookout or guard cells that act as scouts. And so these macrophages are capable of responding directly to an infection to help eliminate an infection but they can also alert other host defenses as well and that is really what makes them sentinel cells. Now there are many different types of macrophages found in different types of tissues and we refer to these macrophages as resident macrophages. And so resident macrophages, as their name implies, they reside permanently in specific tissues, which means that they remain stationary in the tissues and they don't really migrate around to other tissues. They reside in the tissues. And so these red resident macrophages because they reside in the tissues, they will already be present in the tissues. Whenever those tissues get damaged and microbes invade those tissues, they'll already be present and ready to respond because they reside permanently in those specific tissues. Now, other macrophages we refer to as wandering macrophages and as their name implies, they wander around or they move around through the blood to other sites of infection. And so these wandering macrophages can be recruited to a site of infection and again they travel around or wander around through the blood circulate through the blood and they can leave the bloodstream to a site of infection when they are recruited. Now, giant cells refers specifically to macrophages that have fused together and the fusion of macrophages creates these giant cells and the giant cells because they have, they consist of fused macrophages, they have increased destructive abilities. Uh And so if we take a look at our image down below, Over here, on the left hand side, we're specifically focusing in on the macrophages. And so what you'll notice is that here, we're showing you an image of the tissues the skin here and notice that the skin here has been damaged, that there's some kind of damage here and through some kind of sharp object that has penetrated into the skin. And microbes are now infecting this open wound and notice that there are already some macrophages that are present in the tissues already. And we refer to these as resident macrophages because they reside, they are living in the tissues and they're already present and ready to respond whenever any of our tissues get infected. Now, wandering macrophages on the other hand they circulate through the bloodstream. And so as they circulate through the bloodstream they can be recruited to a site of infection. And so the resident macrophages reside and remain stationary within a specific type of tissue. Whereas the wandering macrophage can circulate through the blood and move to other locations and be recruited to sites of infection. Now notice that the second main type of cells that mono sites can develop into are going to be the dendritic cells. And dendritic cells also serve as fake sites but they are mainly going to be important as sentinel cells which again are lookout or guard cells that act as scouts. And so their job is to sense and detect the signs of microbes and then they can alert other immune system cells and activate other immune system cells. So these dendritic cells, they are sentinel cells with long appendages and they reside in tissues and they are capable of alerting and initiating the adaptive immunity and adaptive immune responses and so they can alert and activate B cells and T cells. And so we'll be able to talk more about this process of dendritic cells alerting and initiating adaptive immunity later in our course when we're talking more about adaptive immunity but ultimately hear what we're saying is that um these dendritic cells can ingest pathogens in the tissues and they can ingest those pathogens break them down and then present pieces of those pathogens um to cells of the adaptive immune system in order to activate those adaptive immune system cells. And so once again we'll get to talk more about this later in our course. But down below we're showing you a little image of these dendritic cells. And so these dendritic cells have these long appendages as you see here that project out and here. What we're showing you is an interesting image here is a a micro graph of what these dendritic cells can look like under a microscope. Notice that they have these long appendages that stick out OK? And notice here that we're showing you the intestinal lumen. So this is our intestines, for example, our large intestine and some of the substances that we end up eating get broken down into uh antigens and these antigens could be potentially from microbes that we have eaten. And so what you can see here is that the dendritic cells which are down below. They have these long appendages that can take little samples of the antigens and our intestine and then they can ingest those antigens. Break them down and process them and then present them on their surface. So notice that these little pieces of antigen are presented on their surface. And here's a second dendritic cell doing something similar. And then these dendritic cells can go on to activate other adaptive immune system cells like B cells and T cells which once again we'll get to talk more about that process later in our course when we're focusing on adaptive immune system. But for now this here concludes our brief lesson on the mono sites and how they can develop into macrophages and dendritic cells. And so we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

in this video, we're going to begin our introduction to lymph O sites. And so taking a look at our map of the lesson down below over here on the left hand side notice that the lymphocytes are right over here and they include the natural killer cells, T cells and B cells. And notice that these lymphocytes are all derived from common lymphoid progenitor cells. And so which will notice is that the T cells and B cells are the only lymphocytes that we have listed here that are part of adaptive immunity. However, the natural killer cells, although they are lymphocytes, they are not part of adaptive immunity, they are part of innate immunity. And so notice here that we're saying that recall that these lymphocytes includes Lucas sites that are important for adaptive immunity. But really we're focusing specifically on the T cells and B cells when we're talking about lymphocytes important for adaptive immunity. Now, adaptive immunity is a topic that we'll get to talk a lot more about later in our course and they will be covered in other videos. But really the two major groups of lymphocytes that are important in adaptive immunity are once again going to be the T cells and the B cells and T cells and B cells are going to be lymphocytes important and adaptive immunity And that means that they are both going to respond to very, very specific antigens of invading microbes. And the specificity here is a characteristic of adaptive immunity, but once again, not all lymphocytes are part of adaptive immunity. And so what we need to note here is that however, there are a group of lymphocytes specifically the innate lymphoid cells that differ from the B. And T cells because the B and T cells are part of adaptive immunity. But the innate lymphoid cells are actually part of innate immunity. And so the innate lymphoid cells are commonly abbreviated as I. L. C. S. For short innate lymphoid cells and they differ from the B. And T cells due to a lack of specificity in the antigen recognition. And so whereas T cells and B cells are very very specific and part of adaptive immunity, uh the innate lymphoid cells lack specificity. And so a classic example of I. L. C. S. Or innate lymphoid cells are these natural killer cells or for short, these N K cells or NK s. And uh these natural killer cells are innate lymphoid cells and they kill a variety of different cell types. So they are not specific to one type of antigen. They are going to be uh not specific. And so, taking a look at this image that you see over here notice that we're focusing specifically on the lymphocytes. And once again the lymphocytes include natural killer cells which are innate lymphoid cells that are part of innate immunity but it also includes the T cells and the B cells which are important for adaptive immunity and adaptive immune responses. So once again we'll be able to talk a lot more details about the t cells and B cells later in our course when we're talking about the adaptive immune responses. And we'll also, while we're too talking about the lymphocytes at that time, we'll also be able to talk a little bit more details about the natural killer cells as well later in our course, in those separate videos. But for now this here concludes our brief introduction to the lymphocytes and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.