In this video, we're going to begin our introduction to leukocytes. And so, leukocytes are also known as white blood cells and they can be abbreviated as WB CS. And so these leukocytes or white blood cells play a very important role in immunity to defend our bodies against pathogens or disease causing agents. And so later in our course, we're going to do a very deep dive on immunity in many of its aspects. But for now, we're going to keep the focus specific to leukocytes and some fundamentals that you should know about them. And so, unlike red blood cells or erythrocytes, white blood cells or leukocytes are not actually confined to the blood. And so, although white blood cells can be found in the blood and they can use the bloodstream to travel where they are needed in the body. Many white blood cells or leukocytes can actually migrate out of the bloodstream into the surrounding tissues to perform their functions. And so again, that's unlike red blood cells, which tend to be confined to the bloodstream. Now, leukocytes can broadly be categorized into two major groups based on their appearance under a light microscope. After staining And so these two groups are number one granulocytes and number two, a granulocytes. Now, the granulocytes as their name implies, contain cytoplasmic Granules that are easily visible or easily observed under a light microscope. Whereas the a granulocytes, on the other hand, do not contain easily visible cytoplasmic Granules. And so again, these two groups are based on their appearance under a microscope after staying. Now, what's very important to highlight here is that granulocytes and a granulocytes both contain cytoplasmic Granules. The difference is that the cytoplasmic Granules of granulocytes are easily observed or easily visible under the microscope. Whereas the a granulocytes do not have easily visible cytoplasmic Granules, though those cytoplasmic Granules can still be there. And so let's take a look at our image down below where we can piece some things together. Notice on the left hand side over here, we have the same test tube that we've seen before in our previous lesson videos showing the blood separated out into its three major components, the plasma, the Buffy coat and the erythrocytes. Now notice that the white blood cells are actually going to be present in the Buffy coat region. And so that's why we are highlighting that Buffy coat region to indicate that this is where the leukocytes can be found. Uh Now again, leukocytes are known as white blood cells and they can be abbreviated as WB CS. And again, these leukocytes can be broadly categorized into two major groups based on their appearance under a microscope. After staining, the first major group are going to be the granulocytes, which you'll notice there are three main types of granulocytes. And in all of these granulocytes, you can very easily see the cytoplasmic Granules, these little dots that are throughout them under the microscope after staining. And so notice that we have these interactive blanks for each of these three types of granular sites. And so moving forward, when we discuss them, you can actually come back and fill in these blanks for these three types of granular sites that we'll discuss in more detail. Now, the second major group of leukocytes are going to be again the a granulocytes and notice that there are several different types of a granular sites that we are going to cover moving forward in our lesson. But what you'll notice is that these a granulocytes do not have visible cytoplasmic Granules inside of them, like what you could see over here with these granulocytes. And so really this is what categorizes them into this group, a granulocytes. And again, we have these interactive blinks and as we move forward and discuss more details about these a granular sites, you can come back and fill in these interactive blanks that you see throughout. But for now, this year concludes our brief introduction to leukocytes and moving forward, we'll be able to apply these concepts and learn more about these leukocytes. So I'll see you all in our next video.
2
example
Leukocytes Example 1
Video duration:
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So here we have an example problem that asks which of the following statements about erythrocytes and leukocytes is false. And we've got these four potential answer options down below. Now option A says that leukocytes are significantly larger than erythrocytes. Now recall from back in our previous lesson, videos that erythrocytes are actually relatively small cells only about seven micrometers in diameter and most other body cells are much larger, 2 to 3 times larger in most cases. And that includes the leukocytes. And so to say that leukocytes are significantly larger than erythrocytes. This is actually a true statement and because it's a true statement, it's not a false answer option that we're looking for. So we can cross off option A. Now, option B says that leukocytes and erythrocytes are both confined to the bloodstream during norm normal function. And so of course, we know from our last lesson video that this is actually not true. This is a false statement recall that erythrocytes or red blood cells are typically confined to the bloodstream to perform their normal function. However, leukocytes or white blood cells can actually migrate out of the bloodstream into surrounding tissues to perform their normal functions. And so uh leukocytes are not confined to the bloodstream like erythrocytes are. And so, because this is a false statement, that means that this is the false answer option that we were looking for. So we can indicate that option B is the correct answer to this problem. Now, option C says that erythrocytes primary function is transport while leukocyte's primary function is protection. And of course, we know that this is a true statement and uh we know that erythrocytes are going to function primarily in the transport of gasses such as oxygen gas, for example, and some carbon dioxide gas. And we know that leukocytes or white blood cells, their primary function is in immunity to defend the body against pathogens. And so it does protect the body because this is true. It's not the false option that we're looking for. So we can cross off option C and then of course, because uh option B is false, we can also eliminate option D which says all of the above are true. So again, be here is the correct answer that concludes this problem. And I'll see you all in our next video.
3
Problem
Problem
What differentiates granulocytes from agranulocytes?
A
a) Granulocytes contain cytoplasmic granules, but agranulocytes do not.
B
Granulocytes contain cytoplasmic granules that can be easily visualized under a microscope after staining.
C
Granulocytes are larger.
D
Granulocytes are smaller.
4
concept
Granulocytes
Video duration:
3m
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In this video, we're going to begin our lesson on granulocytes, which are cells of the innate immune system. And so these granulocytes are white blood cells or leukocytes with visible cytoplasmic Granules, which is really implied by their name. You can see the Granules uh within their name. And so these Granules are cell structures that contain compounds that are used for protective functions and are visible under a light microscope. Now, really, there are three main types of granular sites that are named based off of the staining properties of their Granules. And so the first main type of granulocyte are going to be the neutrophils and the neutrophils actually have a nucleus with five lobes. So they have a five lobed nucleus and they have really small Granules which really do not stain very well. And so their Granules remain somewhat of a neutral color, which is why they're referred to as these neutrophils. Now, neutrophils are also sometimes referred to as polymorphonuclear neutrophils because poly is a root that means many and uh morone nuclear is talking about a morphed nucleus. And so uh these are abbreviated as PM NS. And so if we take a look at our image down below. Uh notice over here on the left hand side, we're showing you the granular sites and uh notice that we're showing you the neutrophils on the far left and notice that they have five lobed nucleus and uh their Granules are so small that they don't stain very, very well. Now, the next type of granulocyte that we have here are the eosinophils and the eosinophils have 2 to 3 lobes in their nucleus and they have larger Granules that stain a reddish orange color. And so if we take a look at our image down below, at the eosinophils, notice that their nuclei have uh 2 to 3 lobes and they have these larger Granules that stain a reddish color. And then the last type of granulocyte is going to be the basophils and the basophils have two lobed nucleus and uh they have larger Granules that stain a darker blue uh or purple color. And so if we take a look at the basophils down below over here, notice they have a nucleus with two lobes and they have these larger Granules that stain a purplish bluish color. Now, as we move forward in our course, we'll be able to talk a little bit more details about each of these different types of granulocytes, the neutrophils, eosinophils and basophils. And so this here concludes our brief introduction to the granular sites. And once again, we'll be able to learn more about them as we move forward. So I'll see you all in our next video.
5
concept
Neutrophils
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5m
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In this video, we're going to talk some more details about neutrophils. And so, recall from our last lesson video that neutrophils are one of the three types of granulocytes. And so these neutrophils are the most abundant type of leukocyte or the most abundant type of white blood cell in the blood. In fact, they can make up to 70% of all leukocytes in the blood, which is the overwhelming majority. And so uh these neutrophils, uh they also will be able to migrate to different locations via the bloodstream and uh they are able to respond to a site of infection or tissue damage. And usually they are going to be the first to respond to an infection or tissue damage. So they are going to be the first cells to be recruited to the site of infection or the site of damage. Now, the Granules that these neutrophils contain uh are going to have a variety of different antimicrobial peptides, including defenses as well as hydrolytic enzymes that have the ability to degrade microbes and destroy microbes. Now, the Granules themselves can also be released into the environment and uh this process of releasing the Granules is referred to as degranulation. And uh uh so these Granules, they can either be released through degranulation or the neutrophil could destroy the microbes during phagocytosis. And so, phagocytosis is the process of ingesting and digesting material that has been brought in from the outside. And this includes invading microbes. And so phagocytosis is sometimes referred to as cell eating. Now, another really interesting thing that these neutrophils can do is they can actually release neutrophil extracellular traps or nets which really act as webs of chromatin. So they essentially release their own DNA into the environment to serve as a net or a trap that will once again trap uh infecting microbes in their DNA that they release and trapping the microbes can be an important defense mechanism focusing specifically on these neutrophils at the moment. And so notice that these neutrophils again, they have these five lobes, they have these smaller Granules that do not stain very well. And here's an image of what a neutrophil could look like under a microscope. Now, uh notice that here, we're showing you an image of some kind of sharp object penetrating into the skin and penetrating tissue. And when a sharp object here penetrates into the tissue, it can create uh an area where microbes pathogenic bacteria might be able to enter into our tissues. And so notice that uh neutrophils are usually the first cells to respond to the injury and they're the first cells to be recruited to the site of infection or the site of damage. And uh notice that these neutrophils, they travel through the bloodstream and they're able to leave the bloodstream into the site of infection. Now, these neutrophils are geared to fight the pathogenic microbes to defend us from these pathogenic microbes. And so they can do this either via phagocytosis where they can uh ingest microbes and degrade microbes. They can also like what this neutrophil is doing. They can de granulate, which recall means they can release their cytoplasmic Granules into the environment so that those cytoplasmic Granules can act on those microbes and destroy the microbes. And they can also release those nets or those neutrophil extracellular traps uh or nets that once again serve as webs of chromatin to trap infecting microbes. And so notice here in this image right here, we're showing you a neutrophil that is uh releasing its net, its uh web of DNA to trap the microbes. And so uh these neutrophils, another thing they can do is they can also recruit other immune cells to fight the infection. And so notice that these uh wandering macrophages are also being recruited to this area so that they can also help fight off these microbes that have invaded. And so uh this year concludes our brief lesson on neutrophils and we'll be able to apply some of these concepts as we move forward in our course and also learn about the other granular sites as well, uh, including eos fills and basophils as we move forward. And so I'll see you all in our next video.
6
Problem
Problem
Which granulocyte is the first to respond to an infection, has hydrolytic enzymes in its granules, and possesses the ability of phagocytosis?
A
Basophil
B
Eosinophil
C
Neutrophil
D
Macrophage
7
concept
Eosinophils
Video duration:
1m
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In this video, we're going to briefly discuss eosinophils. And so recall from some of our previous lesson videos that eosinophils are one of the three types of granulocytes. And the primary role of eosinophils is to protect against parasitic worms or helmets. Now, the Granules of these eosinophils actually have antimicrobial substances that bind parasites and they also contain enzymes that disrupt the membrane permeability of those parasites. And so these eosinophils are geared to destroying and killing these parasitic worms or helmets that may try to invade and infect our bodies. Now, eosinophils can also be involved with the sy symptoms uh associated with allergies. And so we'll be able to talk a little bit more about allergies later in our course. And uh again, these eosinophils uh here we're showing you an eosinophil um and these eosinophil is uh going to contain these uh cytoplasmic Granules that can stain a reddish color and they can be released into the environment so that their uh antimicrobial substances and enzymes can help defend against uh parasitic worms such as this helmet that you see right here. And so uh these eosinophils again are important for defending against parasitic worms and helmets and can also be important for some of the symptoms associated with allergies. And so this here concludes our brief lesson on eosinophils. And once again, we'll be able to apply some of these concepts as we move forward. And then we'll get to talk a little bit about the last type of granular site, the basophils. And so I'll see you all in our next video.
8
concept
Basophils
Video duration:
3m
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In this video, we're going to talk some more details about basophils. And so, recall from some of our previous lesson videos that basophils are one of the three types of granulocytes. And so these basophils like eosinophils are also involved in allergic reactions. But the basophils are also really important for inflammation and the inflammation response during an infection. And so these basophils will produce a molecule known as histamine and this molecule histamine is going to be released during inflammation and it will promote inflammation by increasing capillary permeability or the permeability of the capillaries. And the permeability is how easily penetrable it is. And so uh this histamine molecule that is released by increasing capillary permeability, it will allow other defense cells to easily leave the bloodstream and enter into an infected area of the host so that they can help protect and defend the host. Now, mast cells are cells that are very similar in function to the basophils. However, the mass cells are going to be found inside of the tissues. And so they are going to be found in many different types of tissues rather than circulating through the blood, like what the basophils do. And so these mass cells uh are going to be capable of detecting tissue damage, de granulating to release histamine. And again, the histamine can then induce inflammation. And so uh the basophils uh are going to be very similar to the mass cells. Once again, the basophils are going to be in the blood vessels, uh basically uh circulating through the blood. And so over here, on this side of the image, we're showing you specifically the baso fill and the basophil is a granular site. So it's going to have these cytoplasmic Granules that stain a bluish purplish color and they contain histamine and so upon degranulation, releasing this histamine, uh the histamine once again can lead to inflammation. And so notice that the mass cells are going to be very similar to the basophils, except the mass cells are embedded in the tissues. And so you can see here the mass cells embedded in the tissues. And uh again, the mass cells are going to be able to detect specific types of antigens or allergens molecules that can cause allergies. And uh again, they can lead to degranulation and the release of histamine and the histamine can lead to inflammation. And so these basophils, again, they are important for allergic reactions and also important for the inflammation response. And so this year concludes our brief lesson on basophils and mass cells. And we'll be able to get some practice applying some of these concepts as we move forward in our course. And so I'll see you all in our next video.
9
Problem
Problem
Which of the following is a phagocytic cell found in the human body?
A
Eosinophil
B
Neutrophil
C
Basophil
D
T cell
10
Problem
Problem
Which of the following answers are characteristics or roles of granulocytes?
A
Release of hydrolytic enzymes that damage bacterial cell membranes
B
Production and release of histamines which increases capillary permeability
C
Release antimicrobial substances that damage the membranes of parasites
D
Phagocytose invading microorganisms
E
All of the above
11
Problem
Problem
White blood cells are referred to as _____________.
A
Platelets.
B
Erythrocytes.
C
Leukocytes.
D
Megakaryocytes.
12
Problem
Problem
Two immune cells have very similar functions. Both immune cells release histamine and induce inflammation. However, ______________cells reside in specific tissues, while____________ cells travel through the blood stream.
A
Mast cells; Basophil cells.
B
Basophil cells; Neutrophil cells.
C
Granulocyte cells; Basophil cells.
D
Eosinophil cells; Dendritic cells.
13
Problem
Problem
In type I allergic reactions, antibodies are produced and bind to:
A
Mast cells.
B
Neutrophils.
C
Eosinophils.
D
Monocytes.
14
Problem
Problem
Granulocytes:
A
Travel through the lymphatic system.
B
Are the most numerous leukocytes in circulation.
C
Develop in the thymus.
D
Do not contain distinct granules in their cytoplasm
15
concept
Agranulocytes
Video duration:
3m
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So now that we've covered the granulocytes in our previous lesson videos, including the neutrophils, eosinophils and basophils. In this video, we're going to focus in on the a granulocytes. And so recall that the a granulocytes are leukocytes or white blood cells with cytoplasmic Granules that are actually not visible or easily visualized under a light microscope after staining. Now, the a granulocytes are going to include monocytes and lymphocytes and moving forward in our course, we're going to talk more details about each of these different types of a granulocytes. Now, the monocytes are cells that circulate in the bloodstream and they could actually develop into either macrophages or dendritic cells. And again, we'll get to talk more about macrophages and dendritic cells as we move forward in our course. Now, the lymphocytes are going to include B cells and T cells and these cells are specifically involved in adaptive immunity. And so once again, moving forward in our course, we'll be able to do a deeper dive on immunity and talk about many of its aspects including adaptive immunity. Uh But here we're reminding you that this will be covered in later videos and for now, we're focusing in on some fundamentals that you should be aware of when it comes to these a granular sites. So let's take a look at our image down below. And again, we know that this image is showing us the leukocytes or white blood cells, which we know can be broadly categorized into these two major groups, the granulocytes, which we covered in our previous lesson videos and the a granular which we are covering now and again, the granulocytes, you can clearly see those cytoplasmic Granules within uh the cells, those little dots. And with the a granulocytes, notice that you don't see those cytoplasmic Granules inside those cells. Now again, the a granulocytes include monocytes, which we're showing you an image of right here and recall that these monocytes circulate in the blood and can differentiate into either macrophages or dendritic cells. And again, we'll talk about these cells in more detail, moving forward. And then the A granulocytes also include lymphocytes. And the lymphocytes include once again T cells and B cells. And these T cells and B cells are involved in adaptive immunity, which will cover in more detail later in our course. But as you can see here in this image, the lymphocytes also includes these NK cells, these natural killer cells and these cells are considered lymphocytes, but they play a role in innate immunity, not adaptive immunity. And so again, we'll get to talk more details about these lymphocytes later in our course, as we move forward. But for now, this year concludes our brief lesson to a granular sites and I'll see you all in our next video.
16
concept
Monocytes
Video duration:
7m
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In this video, we're going to begin talking about monocytes and the cells that derive from monocytes. And so these monocytes are capable of developing into one of two main types of phagocyte cells or cells that are capable of performing phagocytosis 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, phagocyte cells, meaning that they're capable of performing phagocytosis. And they also serve as sentinel cells, which we call 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 resident macrophages because they reside in the tissues, they will already be pre in the tissues. Whenever those tissues get damaged and microbes uh 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 refer specifically to macrophages that have fused together and the fusion of macrophages uh 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, uh what you'll notice is that here, we're showing you an image of the tissues, the skin here and notice that the t the skin here has been damaged, that there's some kind of damage here. And uh there's some kind of sharp object that has penetrated into the skin. And microbes are now infecting this uh 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 bud and move to other locations and be recruited to sites of infection. Now, uh notice that uh the second main type of cells that monocytes can develop into are going to be the dendritic cells. And dendritic cells are also serve as phagocytes, 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 uh they reside in tissues and they are capable of alerting and uh initiating the adaptive immunity and adaptive immune responses. And so they can alert and activate B cells and T cells. And so uh 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. Uh But ultimately, here, what we're saying is that um these dendritic cells can ingest uh 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 uh here what we're showing you is an interesting image. Uh Here is a um uh a micrograph of what these dendritic cells can look like under a microscope. Uh notice that they have these long appendages that stick out. OK. And uh notice here that we're showing you the intestinal lumen. So this is our uh intestines, for example, our large intestine and uh 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 uh eaten. And so um what you can see here is that the dendritic cells which are uh down below, they have these long appendages that can take little samples of the antigens in 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 year concludes our brief lesson on the monocytes 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.
17
Problem
Problem
All of the following are major differences between macrophages & neutrophils except which of these answers?
A
Macrophages can perform phagocytosis while neutrophils cannot.
B
Macrophages kill microbes by "eating" them. Neutrophils kill microbes with hydrolytic enzymes and/or phagocytosis.
C
Neutrophils circulate the bloodstream while resident macrophages reside in tissues.
D
Neutrophils are granulocytes while macrophages are agranulocytes.
18
Problem
Problem
Monocytes can differentiate into which types of immune cells?
A
Basophils & macrophages.
B
Neutrophils & dendritic cells.
C
Macrophages & dendritic cells.
D
Mast cells & macrophages.
19
concept
Introduction to Lymphocytes
Video duration:
3m
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In this video, we're going to begin our introduction to lymphocytes. Uh recall that these lymphocytes includes leukocytes 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. Uh 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 so T cells and the 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 uh 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 IL CS 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 Il CS or innate lymphoid cells are these natural killer cells or for short, these NK cells or NKS. 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 uh 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 uh while we're talking, 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 year 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.
20
Problem
Problem
Why is a bone marrow transplant used to replace defective lymphocytes in a patient?
A
Bone marrow creates common myeloid progenitor cells which differentiate into lymphocytes.
B
Bone marrow creates monocytes which differentiate into lymphocytes.
C
Bone marrow creates hematopoietic stem cells which differentiate into all immune cells including lymphocytes.
21
Problem
Problem
Which of the following immune cells is NOT a professional phagocyte?
A
NK cells.
B
Neutrophil.
C
Macrophage.
D
Dendritic cell.
22
Problem
Problem
Which of the following are referred to as mononuclear phagoytes?