Since the beginning of time, blood has been an important part of human life. It has been full of mystery, wonder, fear, and concern. And today we're talking about it on Hello from the Van. There's a lot of history, mystery, culture, religion tied with humanity's knowledge of blood. We're actually not going to talk about any of that today because we are only talking about blood types. Did you know that there are eight different types of blood? These eight types are named using a combination of letters and symbols. You can either be O positive, A positive, B positive, or AB, the two letters A and B smooshed together, AB positive. Those are the first four types. Then there's O negative, A negative, B negative, and AB negative. Now that we know the names, where do we get the names from? It all started 125 years ago with an Austrian scientist named Carl Landsteiner in the year 1900. Old Carl was working at a place called the Pathological Anatomical Institute of the University of Vienna. It's just called the University of Vienna now, but it had a longer name back then. And he was running experiments, the way that one does when they're learning at a medical university. And he had a question. Under this question, what happens when you mix blood together? He discovered that when he mixed the blood serum of different people and animals, it would do what's called agglutination, or it would agglutinate. This is just a fancy word for stick together or clot. The trick was that as he did this observation, he didn't know why it would only happen part of the time. He would mix some blood together and it would clot instantly. He would mix other blood together and nothing would happen. It would be just fine. And he didn't know why. Here's a footnote from one of his experiments. Quote: The serum of healthy human beings not only agglutinates animal red cells, but also often those of human origin from other individuals. It remains to be seen whether this appearance is related to inborn differences between individuals or it is the result of some damage of a bacterial kind. Close quote. So basically, Carl's hypothesis was that deadly clumping that was happening could be the result of bacteria, because agglutination or clumping also happens in bacterial cells. These clots that come from mixed blood types are especially dangerous in humans, as getting incompatible blood in your system can lead to death. So this discovery of different blood types was huge. It would be less than a decade before other scientists all across the world were using Carl Landsteiner's research as a basis for their own research and discovery. Carl was actually well on his way to becoming a Nobel Prize winner and the father of modern blood types. You see, by 1901, old Carl had named three types of blood, calling them groups A, B, and C. By 1902, he had recruited help, and he had two medical students, Adriano Sterley and Alfred Von De Castillo, and they had discovered the fourth type, what we now know as type O, but then they just called it a no particular type. By this time, they had also discovered that blood type was genetic and inherited from your parents, and that there are both antibodies and antigens in your blood. In short, they had discovered the eight types of blood. They just didn't realize it yet. So the letter portion of the name, so A, B, O, and AB, all come from things called antigens that are present on blood cells. An antigen is just a substance that makes your body's immune system react. Think of it like your blood is your body's security system and an antigen is like a name tag. So they just have O, A, B, or AB name tags. It's like an ID badge for your immune system. Now, if your body doesn't recognize the antigen present in a blood, it will fight that blood as it enters your system. Basically, certain blood types are given security clearance in other bodies, and some blood types are not. Now hang with me because there's another layer of security clearance in your body, and it's called the rhesus factor. No, not rhesus pieces factor, but rhesus, r-h-s-u-s. In short, we just call it the RH factor. And your antigens are either Rh positive, meaning that they have the rhesus antibody, or Rh negative, meaning that they do not have the Rh antibody. Your blood type being compatible with someone else means that their body recognizes your blood and its antigens and antibodies as safe. That's basically all it is. But how does it work? So we've got our four base antigen types O, A, B, and AB. These antigens have antibodies, positive or negative. I personally am type O positive, meaning I have the O antigen and I am rhesus positive, meaning RH positive. If you are a visual learner, let me tell you how I remember all of this. If you're not a visual learner, please just enjoy this insight into the way that my brain works. I imagine all of the antigens as a fruit. O is oranges, A is apples, B is bananas, and A and A B is jackfruit. I then imagine that these fruits are either wearing a rhesus hat or not, meaning they're wearing the rhesus antibodies or not. Since I'm O positive, I just imagine my blood type as an orange wearing a silly little top hat made of antibodies. And if you think it's confusing now when we know all about it, imagine the confusion in the 1900s when this was emerging research. It was all made even more complicated because Carl and his team at the University of Austria were not the only ones working on blood classifications. By 1907, a Czech scientist named Jan Jansky independently introduced his own blood type names. So he took the research and discovery of Carl Landsteiner and he gave it his own names. Instead of using letters, he decided to give it numbers. One, two, three, and four. But unknown to Yansky, an American doctor named William Moss devised a slightly different classification system using the same numbers. The problem is that his numbers meant different things. So when Yansky was talking about his type 1, what we know as type O, Moss's type 1 was what we know as type A B. They were talking about two different things, but using similar names. This caused confusion and dangerous situations in both science and medicine. And it was happening all over the world. Moss's system was used in Britain, France, and the US, while Yansky's was used in the rest of Europe and small niche pockets of the United States. So in 1921, a bunch of scientists and doctors got together and they said, enough is enough. We're making a joint statement. Yansky's is the proper way to do it. But this recommendation was ignored by the Moss followers. Confusion and danger reigned. So in 1927, remember Carl Landsteiner, the father of modern blood typing? He had moved from the University of Austria to the Rockefeller Institute for Medical Research in New York. As part of this move, he was a member of a committee called the National Research Council, and they had been tasked with learning and discovering more about blood grouping and blood typing. Partly because he was the original guy to discover it, and partly because he was the head of this research, he suggested that scientists and doctors substitute both Yansky's and Moss's numbered systems and go with letters instead. He basically said, listen, none of the previous systems worked. Why don't we come up with a new one? We'll call it A, B, O, and AB. Luckily, everyone agreed. By 1930, he'd won a Nobel Peace Prize, and by the 1950s, his system was universally accepted and practiced around the world. We all still use it to this day, and it's called the Landsteiner classification system. As part of the Landsteiner classification system, we know that certain blood types can donate to other blood types. If your blood type fruit is wearing a hat, you can donate to other blood types that have hats. But like most things in science, there is an exception to this rule. And the exception is type O blood. When Carl and his team discovered type O blood, they called it no particular type because it's basically a blank slate. It doesn't agglutinate with other types of blood. We now call type O negative blood the universal donor type. If you are O negative, you can donate to any other type of blood. I have O positive blood, so I can donate to any of the other types of blood that are RH positive or wearing their silly little hats. O negative blood is very important to the medical community and to hospitals because if you have someone come in with a wound or an injury and you don't have time to determine their blood type, but you know that they need blood, you can give them O negative blood and it will normally be accepted. But here's how things get even crazier. Let's say that a mom who has a negative type blood, so no hat on her antigens, falls in love with a glorious man who just so happens to have Rh positive blood, and they decide to start a family. What if she gets pregnant? And through the power of genetics, her baby has Rh positive blood just like her husband. It can actually be very, very dangerous for both the mother and the child. It's called the RH factor, and it can get worse with each pregnancy as a mom's body says, wait a second, my blood doesn't have hats. Quick, body, make a bunch of hats to compensate. But then it's too much and it becomes dangerous for the mom and the baby. You see, during pregnancy, the blood of the mom and the baby don't normally mix, but sometimes they can during birth or a C-section or other types of complications. If this happens, it can cause bleeding, anemia, blood clots, or even be fatal for the mom and the baby. So if you're a woman with Rh negative blood, there are treatments that you can do. You can have the baby without a hitch. You just have to get the right treatment first. And before we go, we need to talk about percentages. Because yes, there are eight types of blood in this world. But the percentages of each of these types are not equally distributed across the types. There's not an equal amount of people with O positive blood as there are people with AB positive blood. So here's the breakdown. According to Stanford University, O positive is the most common blood type in the entire world, coming in at 37.4% of the world's population has O positive blood. Right behind that, 35.7% of the world's population has a positive blood. This means that you have nearly a 71% chance of being either O positive or apositive. The other six types range anywhere between 8.5 to 3.4% of the world's population. The most rare blood type is AB negative, where one in 167 people or 0.6% of the world's population has AB negative blood. Interestingly, O negative blood is the universal donor type of blood, and A B positive blood is the universal receiver type of blood. If you have A B positive blood, you can receive a blood transfusion or a blood donation from any other type of blood. Well, O negative is the universal donor type. If someone has O negative blood, they can only receive O negative blood. If you still have questions or concerns about who can donate blood to who, I highly, highly suggest that you look up a blood donation chart. But it's all a lot. And in my mind, it is miraculous that something as complicated as eight different types of blood was ever discovered. Science is incredible. And with that, I'm Mimi Fotz, and this has been Hello from the Band.