0:00 On Wonder how to do that, biology and medicine videos, please make sure to 0:03 subscribe during 0:04 the forming group for the latest videos. 0:06 Please visit Facebook on Wonder how to do it again. 0:07 Please like. 0:08 And here you can also ask questions, answer questions and post some interesting 0:11 things 0:11 including your artworks or send them to me please. 0:14 And please change the quality settings to the highest one for better graphics. 0:18 Continuing on with the immunology map, we're looking at part three. 0:21 And so just revising from the very first immunology map, the different leuk 0:26 ocytes, the 0:27 immature and the precursors arise from the bone marrow. 0:31 And they arise from the bone, the cells within the bone marrow known as plurip 0:35 otent stem 0:36 cells. 0:37 So the pluripotent stem cells here give rise to different types of leukocytes, 0:41 immature 0:42 or precursors or even mature ones. 0:45 And these different leukocytes will then leave the bone marrow into the 0:49 bloodstream where 0:50 they will travel to and migrate to specific tissues, organs or they will just 0:56 circulate 0:57 throughout the body, such as the granulocytes. 1:02 An example of this is that the T cell precursor, the lymphoid precursor will 1:07 travel to the 1:08 thymus to become mature, the immature B cell will travel to the lymph node to 1:13 become activated. 1:16 And then in part two, we looked at the different organs and tissues within the 1:22 immune system 1:23 and how the different leukocytes migrate or move into these different tissues. 1:28 The liver, as we have learned, produces important substances for the immune 1:33 system, such as 1:34 the complement proteins, which are important in the innate immune system. 1:38 And then we saw how the some types of leukocytes, such as mast cells and mac 1:43 rophages and dendritic 1:45 cells, move into tissues, such as tissues underneath our skin. 1:50 And they make up the innate immune cells because of the first line of defense, 1:54 you can say. 1:55 And then we stopped where the lymphoid precursor, or we can even now say the T 2:03 cell precursor 2:05 migrates into the thymus here, and this is where we stopped. 2:08 So in this video, we'll actually see what happens to this T cell precursor. 2:14 Of course, because this is a T cell precursor, it will obviously become a T 2:19 cell. 2:20 However, we looked at the lymphoid precursor when it entered the thymus. 2:24 And so this lymphoid precursor, it can be programmed depending on how it was 2:30 programmed. 2:31 It can become a number of different types of leukocytes, including a natural 2:35 kill cell. 2:36 But for now, we are just assuming that this lymphoid precursor will become a T 2:43 cell. 2:44 So we just wrote this up as T cell precursor. 2:47 So in this video, we're going to look at the development of T cell from the T 2:50 cell precursor, 2:51 from the lymphoid precursor. 2:55 So we start off with the T cell precursor. 2:58 The T cell precursor expresses no sign of being an actual T cell. 3:05 A T cell precursor in the thymus will become either a CD8 T cell or a CD4 T 3:13 cell. 3:14 A CD8 and CD4 basically means the type of receptor it will have or it will 3:21 express. 3:22 It will express a CD8 receptor or it will express a CD4 receptor. 3:27 In a T cell precursor stage, it expresses none of these. 3:31 So you write this T cell precursor as CD8 negative and CD4 negative, meaning it 3:37 contains 3:38 no receptors or no T cell receptor, CD8 and no T cell receptor, CD4. 3:44 However, in the thymus, the T cell precursor will become a naive T cell, which 3:51 will then 3:51 express both CD4 and CD8 receptors. 3:55 And so we write this as CD4 plus and CD8 plus because it expresses both of them 4:01 . 4:02 Now this naive T cell which expresses both CD4 and CD8 co-receptors can then 4:07 become specifically 4:10 either a naive T cell which only expresses a CD8 co-receptor or a naive T cell 4:17 which 4:17 specifically expresses a CD4 co-receptor. 4:22 So we write this as a CD8 cell or a CD4 cell. 4:26 So again, this T cell precursor will become either a naive T cell CD8 or naive 4:33 T cell 4:34 CD4. 4:37 You might have remembered me saying that a CD4 cell is a T helper cell and that 4:41 a CD8 4:42 cell is a T killer cell. 4:44 This is true in a way, but because these cells are CD4 and CD8 cells here in 4:50 the thymus 4:51 are still naive, they are still just CD4 and CD8 and they can become different 4:57 types 4:57 of cells later on once activated. 5:00 However, generally a CD4 cell will become a T helper cell and generally a CD8 5:08 cell will 5:09 become a T killer cell once activated. 5:13 And so in the thymus, we saw that a T cell precursor will give rise to either a 5:17 CD8 5:18 or a CD8 cell or a CD4, a naive T cell. 5:21 Now let's look at the immunology map and see how this T cell development occurs 5:26 in 5:27 a bit more detail. 5:31 So this is where we last stopped off where the cell such as the monocyte, dend 5:35 ritic cell, 5:36 immature dendritic cell and the lymphoid precursor cell migrates or moves into 5:42 the thymus. 5:43 Let's zoom into this thymus section here. 5:45 Now this is just a simplified diagram of the inner works of the thymus. 5:50 The thymus consists of the outer cortex and the inner medulla. 5:56 And the corticomodullary junction is what separates the cortex with the medulla 6:01 . 6:01 Surrounding regions within the thymus are known as a capsule. 6:07 Now within the medulla and cortex, we have some cells such as the medulla, we 6:13 have immature 6:14 dendritic cells. 6:16 And also we have blood vessels both in the medulla and in the cortex to bring 6:24 the cells 6:25 into the thymus essentially. 6:27 And also in the medulla, we find what's called the thymic epithelial cells 6:32 which are 6:32 important for the development of T cells. 6:37 In this video, I am not going to include the chemical signals involved in the 6:42 development 6:43 of the T cell. 6:44 I am just going to explain the overview or the overall picture of how CD4 and 6:50 CD8 T cells, 6:51 the NIFT cells develop.
