 Hey everybody, Dr. O'Hare. This video I want to talk about are blood types. So we're going to focus on the ABO blood typing system, but I'll also mention the RH blood typing system. Just so you know, there are dozens of different antigens and different blood typing systems. I think the Lewis system is one they might look for when you donate plasma. There's one called Duffy. They're kid, I think with 2Ds, doesn't really matter. But there are lots of blood types, blood typing systems, but these are the ones that seem to matter in the huge majority of the time. Alright, so let's look at, so with the ABO system, you can be one of four different blood types, A, B, AB, or O. And so if you have type A blood, that means you're going to have the A antigens on the surface of your red blood cells, and you're going to have the anti-B antibodies in your plasma. And as you can see from this image here, anti-A and anti-B antibodies are IGMs. That's why they have that cool starburst pentamer shape. If you have type B blood, you're going to have B antigens on the surface of your red blood cells and anti-A antibodies in your plasma. If you have type AB blood, you're going to have both the A and B antigens on your red blood cell surface. You will not have any of these antibodies, anti-A or anti-B. We'll come back to why not. And then type O. O, there really isn't an O, there isn't an O antigen. O is the absence of A or B. So if you don't have the A or B antigens on the surface of your red blood cells, you will have both the anti-A and anti-B antibodies in your plasma. So okay, so why does this matter? The main reason you have to know what somebody's blood type is, is to make sure that if you give them someone else's blood that it's compatible. So let's talk numbers here first to actually, we better talk about the RA system next as well. So AB, AB and O, that's determined by the presence or absence of A and B antigens, but there is also RH antigens. So it used to be called D when I was in college, but now you hear it called RH. RH stands for Rhesus, the type of monk you did this research on. So whether or not you have RH antigens on your red blood cell surface determines if you have a positive or negative blood type. So when they give you your blood type, they're telling you the ABO system, then they put a positive or negative on the end of it, which is telling you your RH blood type as well. So for example, if you're A positive, that means you have this type A blood that you can see here, plus you would also have the RH antigens on the surface. So that's so it's the, it's the antigens on your red blood cell surface that determine your blood type. So let's talk about a few numbers. So the overwhelming majority of humans are RH positive, meaning they do have the RH antigens. So the Caucasians are the smallest group with 85% of people being RH positive. African Americans would be 95%, Hispanics are low 90s. Some groups are 100% RH positive. So most human beings do have positive blood types. And then as far as the ABO system, type O is going to be the most common in all groups. And then A and B are going to be the second and third most common. And AB is going to be the least common. So that means that the most common blood type in America then would be O positive. And the least common blood type in America then would be AB negative, just FYI. All right. So what matters more? The antigens on your surface or the, or the antibodies in your plasma. The antigens matter the most. And that's because if, when you get someone else's blood, the tiny bit of antibodies that would come into the system are going to be diluted with your five to six liters of blood that you have. So, the blood, so when it comes to blood typing and compatibility and giving you someone else's blood, the, the antigens on the surface are what matter the most. All right. What else here? Let's talk about universal donor and universal recipients. As you can see here on the, on the bottom of the AB column, type AB blood is the universal recipient. Now, AB positive would be the true universal recipient. And that's because there wouldn't be any antibodies in their plasma. They, they can't have anti-A antibodies or it would attack the A antigens on their own blood cells. They can't have anti-B antibodies for the same reason. And they also can't have anti-RH antibodies for the same reason. So, so they wouldn't have any antibodies. So they are the universal recipient. That means if you have AB positive blood, you can receive blood from anything because you don't have antibodies that would attack any of the other blood types. Now on the flip side, O and really more specifically O negative would be the universal donor. So that means because they don't have and they wouldn't have AB or RH antigens on their surface, you can give O negative blood to anybody. So that's very, very important. So note that AB positive universal recipient can receive blood from anyone. O negative is the universal donor and they can give blood to anybody. But look at, look at how, look at the different compatibility types here because if you're the universal recipient, you can receive blood from anyone, but think, but look at the list here. You can't give the blood to anyone else. If you have AB positive blood, you can't give it to anyone with AB or O blood and you can't give it to anybody else that's AB negative either. So the universal recipient is great if you have that blood type, but you can't give that blood to anybody else. On the flip side, if you're the universal donor, that's awesome, but if you have O negative blood type, the only blood you can receive is O negative blood. So it's, so it's harder to find blood for you, but you can give your blood to anyone. All right. So the, so the compatibilities just, just think about the, the antibodies here. So if you have type A blood, you can receive type A blood or O because O doesn't have any of these, these, the, the wrong antigens, so it doesn't have any at all. So you can get type A or O blood. If you have type B, you can get type B or O blood. If you have AB, then you can get any of them, AB, AB or O, but if you have type O blood, you can only receive O. So the big difference, why do we separate the ABO system and the RH system? Here's the key difference. If you have type A blood, you already have anti-B antibodies. We're not exactly sure why, but, but you have them. It seems to be innate. If you have an RH negative blood type, if you have a negative blood type, you do not have anti-RH antibodies until you've been exposed. So I guess that means technically, if you have O negative blood, you know you've never been exposed to a positive blood type before. And someone, and they accidentally gave you O positive blood, it shouldn't really cause a problem. But now your immune system has seen the RH antigen. You will now have anti-RH antibodies. If that happened the second time, you'd be in deep trouble. So we'll come back and talk about that more when we talk about hemolytic disease of the newborn because that's a condition that only affects the second pregnancy because the first one was when it was sensitized. So that's going to be the key difference. All right. I think that's all the most important stuff here with blood types. We'll talk about actual blood typing and what happens when you get the wrong blood in a separate video. We'll talk about hemolytic disease, the newborn in a separate video. So I guess just one last thing about the genetics of blood type, like where your blood type comes from. So it would be an example of co-dominance. So A and B antigens or the genes that lead to A and B blood types are both co-dominant, which means that they both dominate O, but they can't dominate each other. So if mom and dad both gave you an A gene, then you would have type A blood. But if mom gave you an A and dad gave you a B, you would have the type AB blood. So the only way that you can have type O blood is if mom and dad both give you the gene for the O antigens. So the genetics there is kind of interesting as well. All right. I think I'll probably have to cover that a little bit more detail later. Okay. Have a wonderful day. Bye.