0:00 Armando Hassurungan biology and medicine videos, please make sure to subscribe, 0:05 join the forum 0:05 and group for the latest videos, please visit Facebook at my Instagram, please 0:07 like and here 0:08 you can also ask questions, answer questions and post some interesting things, 0:11 including 0:11 your artworks, or send it to me, please, and you can also please change the 0:15 quality settings 0:16 to the highest one for better graphics. 0:18 These series of videos will look at the immune system as well as the lymphatic 0:22 system to some 0:23 extent, and so I named these series of videos the immunology map, because we're 0:27 concentrating 0:28 predominantly on the immune system. 0:31 And so to study the immune system, we have to know about the immune cells, 0:35 where do they 0:35 come from and where do they go. 0:38 So in this video, we'll concentrate on the immune cell specifically, and to 0:44 learn about 0:45 the immune cells, we have to start from where they came from, which is the bone 0:49 marrow. 0:50 So before looking at the main big map, we're just going to draw a small map and 0:54 look at 0:55 the overview of what we're actually going to learn today. 0:57 So the bone marrow, we have what's called stem cells, and these stem cells 1:01 produce precursor 1:03 or immature leukocytes, the white blood cells. 1:06 And once these white blood cells are there, in the bone marrow, they will leave 1:10 the bone 1:10 marrow into the bloodstream over here. 1:13 And the leukocytes will migrate to different areas, different tissues for 1:17 further maturation 1:18 or for further activation, for example. 1:21 And for an example of this is the precursor T cell, which matures in the thymus 1:28 and the 1:29 immature B cell, which goes to the lymph nodes to become activated. 1:35 Now let's look at the big immunology map now. 1:38 Remember, the previous diagram was just an overview to see what we're going to 1:42 learn 1:43 in this video, this part one. 1:46 So we begin with the bone marrow, where the leukocytes come from. 1:50 The bone marrow is important, it's part of the lymphatic system. 1:54 And it contains cells known as the pluripotent hematopoietic stem cells. 2:00 And these cells, these pluripotent stem cells, these cells are the ones that 2:04 give rise to 2:05 the immune cells, including red blood cells as well. 2:10 What happens actually is that these pluripotent stem cells divide to produce 2:15 two types of 2:16 cells. 2:17 It divides to produce either the lymphoid progenitor cell, which later will 2:20 mostly give rise to 2:22 cells part of the adaptive immune system. 2:25 Or the pluripotent stem cell can divide to produce the myeloid progenitor cell. 2:31 And the myeloid progenitor cell will later typically produce immune cells, 2:35 which would 2:36 be part of the innate immune system. 2:39 So now for simplicity, let us begin with the myeloid progenitor cell. 2:44 And what these cells can give rise to, can divide and give rise to. 2:48 So firstly, the myeloid progenitor cell can divide to give rise to what's 2:52 called an erythroblast. 2:54 And erythroblast can later give rise to a reticulocyte. 2:58 The reticulocyte will then leave the bone marrow and circulate in the 3:01 bloodstream, where 3:02 later on, it will mature to become an erythrocyte or red blood cell. 3:07 And a red blood cell is important for our body, because the red blood cells, 3:11 the erythrocytes, 3:12 is what carries oxygen, transports oxygen to different tissues and removes 3:17 carbon dioxide 3:19 from our body to be exhaled out. 3:22 The myeloid progenitor cells can also divide to produce what's called a mega- 3:26 carriote blast, 3:28 which will later give rise to a mega-carriote. 3:30 This mega-carriote will actually still stay in the bone marrow, but will sec 3:35 rete molecules 3:36 known as platelets and platelets play a critical role in the immune system, in 3:41 that it is 3:42 important in initiating hemostasis and repairs of tissue, for example. 3:47 And they circulate all around our body, by the way. 3:51 Before I continue, it should be noted and stressed that I'm not including all 3:53 the names 3:54 of all the types of cells that will give rise to each of the immune cells. 3:59 I'm only including the names of a couple of cells for simplicity. 4:04 Anyway, continuing on, the myeloid progenitor cell can also give rise to what's 4:08 called 4:08 the myeloid blast, and the myeloid blast can give rise to a variety of cells, a 4:12 variety 4:12 of cells. 4:14 And these variety of cells include a group of cells known as granulocytes, and 4:19 granulocytes 4:19 are special because these are cells which contain granules, hence the granuloid 4:26 before 4:26 the site. 4:28 And the three granulocytes, which will be produced in the bone marrow, are the 4:33 band 4:33 basophil, the band isinophil, and the band neutrophil. 4:39 Other cells that the myeloblast will produce, that is not a granulocyte, is the 4:45 mass cell 4:45 precursor and the promonocyte. 4:51 Whenever a cell has a precursor or a pro within it, it means that it's not yet 4:57 that particular 4:58 cell yet. 4:59 So for example, the mass precursor means that it's not a mass cell, but it will 5:04 become 5:04 a mass cell. 5:05 And the promonocyte means that it's not a monocyte yet, but it will become a 5:10 monocyte. 5:11 So what will happen to these cells, or will become these cells when once they 5:15 leave the 5:15 bone marrow? 5:16 Well, the band basophil will become a basophil once it enters the bloodstream. 5:21 And the role of basophils is to promote allergic responses, and they are 5:24 important for defense 5:26 against parasites. 5:27 The band isinophil, similarly, will become an isinophil. 5:31 And the isinophil role is that it kills antibody-coated parasites, essentially, 5:36 so they're important 5:37 against parasites. 5:38 The band neutrophil will become a neutrophil once enters the bloodstream. 5:44 And the neutrophils are the fast-acting one, and they essentially go into the 5:48 site of inflammation 5:49 or site of damage, the quickest, and it's the most abundant leukocytes. 5:55 These neutrophils are also known as polymorphic leukocytes, because they 6:00 contain many nucleuses. 6:02 Three. 6:03 Now, these are the three granular sites, and as you can see, when in the bone 6:08 marrow, 6:08 their granules are not present yet, but once they're in the bloodstream, they 6:13 have these 6:14 granules, and so they're ready. 6:16 And these granular sites, they typically circulate through the bloodstream and 6:19 essentially 6:20 wait for a particular response, or chemicals, to signal them to go to an area 6:27 where they 6:28 are needed. 6:29 Now, the nongranular sites, the mast cell precursor, when it leaves the bone 6:33 marrow, 6:34 it will still become a mast cell precursor. 6:37 But it will become a mast cell once it enters tissues. 6:43 These granules, interestingly, contain also granules, but they are not part of 6:48 the granular 6:49 site group. 6:51 Why? 6:52 Well, it's because they, muscles, do not circulate, like the mesophils and neut 6:57 rophils. 6:58 They stay in the tissue. 7:00 The other type of cell is a promonocyte, which when it leaves the bone marrow, 7:03 it will become 7:04 a monocyte. 7:05 And a monocyte will circulate around the bloodstream, but when it enters 7:09 tissues, it will become 7:10 a macrophage. 7:11 So in the bloodstream, it's a monocyte, in the tissues, it's a macrophage. 7:15 And macrophages, as we all know, are antigen-presenting cells, and it also eats 7:22 up pathogens. 7:23 Now finally, the myeloid progenitor cell can also give rise to immature dend 7:30 ritic cells. 7:31 And immature dendritic cells, once it leaves the bone marrow, it will still 7:34 become an immature 7:35 dendritic cell. 7:36 A dendritic cell role is important because it is the connection between the 7:42 innate and 7:43 the adaptive immune system. 7:46 Its role is to enter tissues, the peripheral tissues, and then uptake antigens 7:53 from the 7:54 peripheral tissues, and then present them as antigen-presenting cells to the 8:00 adaptive 8:01 immune cells. 8:02 And so the dendritic cells, as I just noted, is important because it connects 8:07 the innate 8:08 immunity and the adaptive immunity, and we'll learn about the dendritic cells a 8:12 lot more 8:13 later on. 8:14 Now let's look at the lymphoid progenitor cells, which also came from the plur 8:20 ipotent stem cell. 8:22 Now the lymphoid progenitor cell, as I mentioned earlier, typically gives rise 8:26 to the adaptive 8:27 immune cells. 8:28 This is true in a way. 8:31 First of all, the lymphoid progenitor cell will give rise to two cells which 8:35 are not really 8:35 part of the adaptive immune system. 8:37 These cells are also the immature dendritic cell, which as we talked about is a 8:41 connection 8:41 between the innate and the adaptive immunity, and the lymphoid progenitor cell 8:44 will also 8:45 give rise to immature natural killer cell. 8:49 An immature natural killer cell, when it leaves the bone marrow to the 8:52 bloodstream, it will 8:53 become a natural killer cell. 8:55 So a killer cell is important, they are large granulated cells which kill 9:01 abnormal looking 9:03 cells or abnormal cells, such as tumors, and they're also important against 9:07 infections. 9:08 What's crazy about them, or why they are called natural killer cells, is 9:12 because they 9:13 kill cells naturally without the need of other signals from other cells. 9:19 So when they see something bad, they will just kill it. 9:24 Now let's talk about the main adaptive immune cells. 9:28 So the lymphoid progenitor cell will give rise to a lymphoid precursor. 9:34 Now this lymphoid precursor will then leave the bone marrow and will still 9:37 become a lymphoid 9:38 precursor, but it will travel to the thymus and will mainly become a T cell. 9:46 So it becomes a T cell in the thymus. 9:49 So okay, why doesn't this cell just be called the T cell precursor, or the 9:55 immature T cell? 9:57 Well this is because the lymphoid precursor can actually also give rise to 10:02 other types 10:03 of cells in the thymus, but it will mainly give rise to T cells because we need 10:08 T cells 10:09 in our body. 10:10 Okay, I hope you understood that. 10:12 Now the lymphoid progenitor cell will also give rise to B cell precursors, 10:17 which will express 10:18 once in the bloodstream only IgM antibodies. 10:22 So now, because it is an immature B cell, it's still not activated. 10:27 A B cell, when we think of B cells, we think of antibodies because later on 10:32 when the B cell 10:34 is activated and it matures, it can become two types of cells, plasma cells or 10:39 memory 10:39 cells, which if it's a plasma cell, it will be able to secrete antibodies. 10:45 And these two types of cells, the memory cells and the plasma cells are an 10:48 important part 10:49 of the adaptive immune system. 10:51 And we'll talk about these cells later on if you don't understand it. 10:56 A point to make is that the T cell, the soon-to-be T cell and the B cell are 11:02 the two important 11:04 lymphocytes, which are part of the adaptive immune system. 11:10 Another interesting thing is that the natural killer cells here, they can not 11:14 only arise 11:14 from the bone marrow, but they can also arise from the thymus, from the lymph 11:19 oid precursor 11:19 cell, which will travel to the thymus, and that's something interesting to note 11:24 . 11:24 But we'll just say for now that the natural killer cells come from the bone 11:29 marrow. 11:30 And so looking back at this small diagram, we learned how the stem cell 11:34 produced many 11:34 types of leukocytes, precursor and immature ones, and that it will go into the 11:39 bloodstream. 11:40 And in the bloodstream, it will travel to different tissues. 11:44 In the next video, part two, we will look at where some of these immune cells 11:48 will travel 11:48 to, the different tissues it will go to, and we'll learn about other organs 11:53 which are 11:53 part of the immune system and the lymphatic system.
