Health and medicine
- Role of phagocytes in innate or nonspecific immunity
- Types of immune responses: Innate and adaptive, humoral vs. cell-mediated
- B lymphocytes (B cells)
- Professional antigen presenting cells (APC) and MHC II complexes
- Helper T cells
- Cytotoxic T cells
- Review of B cells, CD4+ T cells and CD8+ T cells
- Clonal selection
- Self vs. non-self immunity
- How white blood cells move around
- Inflammatory response
- Blood cell lineages
Discover the origins of blood cells in the bone marrow and the role of the pluripotent hematopoietic stem cell in creating all 10 types of blood cells. Explore the myeloid and lymphoid lineages, and learn how these precursor cells contribute to our immune system and overall health. Uncover the surprising connections between different types of blood cells. Created by Patrick van Nieuwenhuizen.
Want to join the conversation?
- I thought that t cells came from the thymus(17 votes)
- No. T cells come from stem cells located in the bone marrow. When the stem cell is differentiated into a T cell, the t cell migrates to the Thymus, where it will continue and complete its training as a T cell.(93 votes)
- At6:00he did not get the change to say what mast cells do? Are their function not so important? Also why were suppressor T cells not mentioned in any of the videos in this section?(15 votes)
- Mast cells have couple of ways to participate in the defence against pathogens. They are phagocytes and like other phagocytes they eat pathogens and presents their antigens to T cells. Therefore they're also antigen presenting cells. They alop release cytokines, such as chemokines that contributes to chemotaxis and other cytokines that increases the permiability of local blood vessels. In that way they contribute in recruiting immune system cells to the inflammatory site.
As far for why regulatory T cells are not mentioned, it may be because this is a simplified introduction to immunology, although they should have been mentioned because they play crucial role in the maintenance of immunological tolerance.(17 votes)
- Is there a distinguishing feature that shows whether a specific dendritic cell is originated from Myeloid or lymphoid progenitor? in other words, how can we identify a dendritic cell that originated from Myeloid progenitor from a lymphoid dendritic cell ?(15 votes)
- According to the study done on mice, CD8α+ and CD8α− DCs derive from a common lymphoid precursor
2 types of dendritic cells were tested:
CD8α+ Dendritic Cells: lymphoid-derived
CD8α− Dendritic Cells: myeloid-derived
Back story on why they were found to be different:
The fact that lymphoid-derive dendritic cells generated along with T cells after intrathymic transfer of CD4low precursors (without myeloid reconstitution potential), led to the widely held hypothesis that CD8α+DCs were lymphoid-derived DCs
Also CD8α− DCs were not found in the progeny of CD4low precursors transferred intravenously, so they were considered as myeloid DCs.
The study's results reveal that CD8α+ and CD8α− DCs derive from a common precursor because both CD4low precursors and BM precursors generated the two DC types at a similar CD8α− DC-to-CD8α+ DC ratio than that existing in nonreconstituted control spleens.
But the differences are noted as follows:
CD8α+and CD8α− DCs differ in their location, migratory capacity, T-cell stimulation potential, and phenotype. The differences explained:
Located in the T-cell zone of the white pulp
more efficient in producing interferon-γ in response to IL-12 during bacterial infection
located in the marginal zone bridging channels and extend from the marginal zone into the red pulp
DCs have a higher phagocytic capacity
- Do dendritic cells function differently depending on their lineage? If not, then what's the point of making them two different ways?(4 votes)
- This is a really good question, and the answer is not totally clear yet: different experts still have different view points.
One theory is that the myeloid and lymphoid lineages actually converge at the point of a 'common DC progenitor' cell, a kind of pre-DC which then goes on to differentiate into many specialised types of DC cell. This challenges our whole concept of distinct lineages, proposing that cells might possess more flexibility than we traditionally assume.
If you want to find out more about DC lineages, I'd recommend 'The Dendritic Cell Lineage: Ontogeny and Function of Dendritic Cells' (Merad 2013), which has extensive lineage detail.(7 votes)
- In studying hematology, I've come across something weird. It seems like a lot of people agree that lymphocytes are produced in the lymph nodes. Is this just a common misconception?(3 votes)
- I think so. They share a similar name, and we talk about lymph nodes and lymphocytes (white blood cells) when we address ill individuals. All blood cell types begin in the bone marrow, which I think also throws people. But thats where all blood lineages originate! The only thing that breaks the pattern is that T cells migrate to the thymus from the bone marrow to mature when we are children. The thymus degenerates as we reach adulthood and beyond.(6 votes)
- what does NK cell stand for ?
what is its function?(3 votes)
- 3:55in the video he says it functions in the immune system. A NK Cell stands for Natural killer cells. They are a type of lymphocyte which is a type of white blood cell that works in the immune system. NK cells play a part in the rejection of both tumours and virally infected cells. They basically kill off infected cells and cells that could harm the body. They are very important for the immune system and how well it functions.(4 votes)
- what are M cells used for in the bone?(4 votes)
- M cells are antigen-presenting epithelial cells found in Peyer's patches (lymphnodes in the intestine). However, they aren't found in the bone. Perhaps you are confusing them with some other cells?(2 votes)
- Do pluripotent hematopoetic stem cells divide or turn into other types of blood cells?(4 votes)
- Yes, they can do both. They can divide and reproduce themselves. They can also divide into more specific cells along a cell pathway.(1 vote)
- Shouldn't the label be: Multipotent Hematopoietic Stem Cell instead of Pluripotent Hematopoietic Stem cell?
Pluripotent cells can give rise to all of the cell types that make up the body; embryonic stem cells are considered pluripotent. Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells; adult stem cells and cord blood stem cells are considered multipotent.
Reference: https://stemcell.ny.gov/faqs/what-difference-between-totipotent-pluripotent-and-multipotent(2 votes)
- The narrator explained that all blood cells came from a precusor cell called pluripotent hematapoietic stem cell, but in the previous blood lineage video he said it is omnipotent hematapoietic stem cell. Which is the correct one? Pluripotent or omnipotent?(1 vote)
- Actually it should be multipotent or progenitor I believe, but it is not very important, just understand they have the ability to make several lines of cells. https://en.wikipedia.org/wiki/Cell_potency
This article explains it very well. Really there are several terms that define the ability of a stem cell to create different cells and tissues. After fertilization, the zygote multiplies and differentiates so that by the time the structure implants into the uterus, the cells have differentiated and lost some of their ' potency' or ability to become any tissue type. In summary, cells developing in a zygote to a morula have the potential to become a whole new individual and make all the tissues, they are totipotent. (Division or separation of the morula results in identical twins.) Then the inner cell mass of a blastocyst differentiates to endoderm, mesoderm, ectoderm and those cells will create several tissues within those layers, they are pluripotent. The cells that can make only cells of one tissue or lineage are multipotent, that describes blood stem cells or hematocytoblasts. (Sometimes the term progenitor is also use for stem cells of a particular tissue.) Cells that can divide to make more of that particular cell are unipotent(2 votes)
Voiceover: All over our body we have blood vessels and in those blood vessels we've talked about how we have lots of different kind of blood cells. We have some red blood cells that I'm drawing here. But if you watched our immune system videos you'll also know that we have some T-Cells and some B-Cells and some macrophages and some platelets. And all in all actually there's pretty much 10 different kinds of blood cells that we have in our blood at all times. In this video I'd like to talk a little bit about where they're made, which you might already know. And also from what precursor cells they're made, because cells don't just come out of nowhere they come from precursor cells that divide and produce new ones. So do you know where all these cells come from? Where they're made? I'm going to draw the answer cartoonish as always and not to scale with this blood vessel. So here's a bone and the answer is that all these cells come from the bone marrow, which is inside the bone here. Voiceover: Now when I first heard this I thought to myself, "How is it possible that blood cells come "from inside the bone, get through the surface "of the bone and get into blood vessels?" Well you might be surprised to know that all these bones are actually profuse with blood vessels themselves, they're very small and difficult to see. So it's actually quite easy for cells to hop into these blood vessels and go into blood vessels of the body. But now let's talk about those precursor cells. So it turns out and this is something that we didn't know for a long time. But it turns out that there's one powerful stem cell in your bone morrow that can make all 10 kinds of blood cells and that one cell, that very powerful cell, has a bit of a complicated name which we'll write out here. It's called a pluripotent ... Pluripotent if you're good with your latin you know that this means, I guess, "Able to do a lot of things." That might be a poor translation but anyway. Pluripotent hematopoietic because hematopoiesis is the process of producing blood cells. So that's pluripotent hematopoietic stem cell. Because Stem Cells as you may know are cells that can divide into multiple different kinds of cells. And now I'd like to ask you a question which is, do you think that a macrophage which, if you watched the immunology video as you know, is a big phagocytic cell so it's like to swallow invaders or debris, do you think that the macrophage is more closely related to a B-Cell which as you know produces anti-bodies or a red-blood cell? You might be surprised by the answer. The answer is actually macrophage is more closely related to the red blood cell, which is kind of weird because macrophages and B-Cells are both immune cells. And red blood cells are not. This pluripotent hematopoietic stem cell gives rise to two main lineages and I'll draw them here. The first is the myeloid lineage ... And the other is the lymphoid lineage. So when this pluripotent cell here first divides, It can give rise to one of these or one of these. And these are also precursor cells to the 10 kinds of red blood cells that we actually find in our blood. So these are not the ones that are going to end up in our blood, these are guys who sit in the bone marrow and make the cells that end up in our blood. So now it turns out that this lymphoid progenitor cell can make actually three different kinds of immune cells in our body, it makes an NK cell ... It makes a B cell ... And it can make a T Cell. And this is three out of our ten blood cells that we talked about and so the other seven are going to be from the myeloid lineage. And one of those is, as you could've guessed ... The red blood cell. Another is the megakaryocyte which you may not remember what it does so I'll tell you in a moment but try to remember. The megakaryocyte is actually what makes platelets. So the megakaryocyte buds off little pieces of it's cytoplasm surrounded by membrane and these are platelets. But the myeloid lineage also makes a bunch of immune cells in addition to the red blood cells and the platelets. And you may not have heard of these, so I'll just list them here. One of them is the neutrophil, that one you're most likely to have heard of and there's two other cells which are very similar to the neutrophil, one is called the basophil ... And one is called the eosinophil. And don't feel too bad about not having heard about these because they're actually pretty rare in your blood, they are there, but there aren't many of them. And then there's also a monocyte which is fairly similar to these three above and the monocyte is actually what becomes a macrophage later on. You're probably familiar with macrophage, a monocyte is just a slightly less differentiated version of a macrophage. And finally, there's also mast cells. And mast cells are the ones that ... So these are our seven other cells ... and as you can see what we said in the very beginning is in fact true. The red blood cell is more closely related to the monocyte or the macrophage than is a B cell or a T cell or something like that. And now I'm adding an addendum to this video to mention one other kind of cell that we've talked about in the past videos but that I didn't put on this chart. And that kind of cell is the dendritic cell, it's one of the antigen presenting cells that we talked about and I want to ask you, do you think the dendritic cell comes from the myeloid lineage or the lymphoid lineage? And it's actually a trick question because the answer is it comes from both. So we have some dendritic cells that I'm drawing here, which come from the myeloid lineage. And some which I'm drawing right next to it which come from the lymphoid lineage. And it turns out that the ones that come from the myeloid lineage are created from monocytes whereas the ones that come from the lymphoid lineage are not really descendants of B or T cells, they come from some lymphoid precursor. So dendritic cells are kind of a weird exception they can be made from either line and I wanted to add yet another piece of information hopefully not overloading this too much just to remind you once again that monocytes in addition to becoming dendritic cells can also become macrophages. And macrophages we are certainly familiar with, At least we've talked about them in the other videos. So here's a macrophage, and macrophages if you remember are kind of like sentinels, they sit out in the tissues and watch for invaders and dendritic cells also behave like that. So what about this monocyte? Does he do the same thing? Well actually no, it turns out the monocyte is kind of like a circulating version of macrophages or dendritic cells. So what do I mean by circulating? I mean that it's actually in the blood. So monocytes move around in the blood and then when they go into the tissues to settle down and become sentinels, that's when they are turned into either macrophages or dendritic cells.