 Is this the end of the story with blood type? No, most of us know that in addition to the AB blood typing, I have type O blood, but I also know that I'm actually O positive and some people are negative, so this person might be AB negative. Negative means the absence of the Rh antigen. So a person who has type negative blood has no Rh antigen embedded in their blood cells. What is my O positive blood going to look like? It's going to have a little Rh... Okay, we're going to make it into a triangle like that. That's a little Rh antigen embedded in the red blood cell. So an O positive human has no A antigens or B antigens, so they have type O blood, but if they do have Rh antigens, then they're O positive. Now, that should make you think, tell me about the antibodies that are associated with the Rh factor. And in fact, there are. There are antibodies associated with Rh and they're anti-RH. In fact, they actually call them anti-Ds, which I'm not sure why that's the case. Oh, man, look, I did it. Whoa, I couldn't visualize which way the antigen would fit into my antibody, but I just did it. If I have a shape on the end of my antibody that's going to match the Rh antigen, then this is going to be anti-RH. And like I said, clinically they call it anti-D and I don't know why. So here's the interesting thing. Anti-A and anti-B antibodies are a specific kind of antibody called type M antibodies, so we can call them IgM antibodies. M for massive, that's a hint. And the type, the Rh antibodies are a different kind of antibodies called IgGs. Ig, oh, I kind of want to say Ig, gigantic, they're tiny, Ig like G, G dog pound, little dog pound, G dog. The Ig antibodies are much smaller than the IgM antibodies. Now here's the scoop. IgM antibodies are so big that they cannot cross the placenta. What? Can't cross placenta. And here's, like, who cares? Well, you would care because if you have a different blood type than your baby in your belly, then your antibodies potentially could cross the placenta and attack your baby because that baby isn't you. It's a parasite. Let's kill it. That's why the parasite in your belly actually does produce immune system suppressants to try and say, dude, ma, quit trying to kill me. I know I'm not you, but I'm kind of like half you, so it's kind of in your best interest to quit trying to kill me. The sad story is that IgGs can cross the placenta. So let's draw a picture. Are you ready? Here's a mama. Look at her. She's not feeling so hot because this is how big she is and she's about to burp out a kid. This is her uterus and this is how big it is. And guess who's living in there? Little punk parasite. Little punk parasite's happy as a clam because this little parasite has totally taken over its mama's entire body. How did it do that? Well, it's the magic of the placenta. I pick on the parasites all the time, but dude, it's so unbelievably cool what they do to hijack our bodies and make it so that we do not kill them because we would. Here's a placenta right here. Placenta's holy shocking structure. If this right here is a uterus where baby grows, baby's first apartment, then the placenta grows from baby tissue and mama tissue. So the baby hijacks the mama's uterus and basically takes a part of it and combines it with baby cells and makes this unbelievable organ called the placenta. Now, mama has a heart. It's probably the only reason why the baby survives and her blood comes into the placenta and dude, it's like a special delivery. I'm going to bring all my best fresh oxygen and all the delicious ice cream and abalone that I just ate and I'll take it back and get rid of it for you. Like no problem, go ahead and just dump your crap kid and it's the beginning of how things roll. Now, mama blood and baby blood never mixes. Tell, are you ready for this? Sorry ladies, if you have not yet spawned parasites out of your uterus. Once you do push that little parasite out of your body, okay, in this direction, bye-bye. The placenta rips off of the wall of the uterus and it's pretty much guaranteed that there will be a bloody mess of bloody hell that happens when the baby gets pushed out and blood will mix. Who cares? Like seriously, nobody cares unless mom is RH negative. She does not have anti-RHs on her red blood cells. Let's just say she's O negative just for the ease of life. What you should probably be thinking is dude, maybe she has some anti-A's if she's typo blood. She has some anti-B's and she also might have some anti-RHs. I'll tell you right now, she does have anti-A's. She does have anti-B's. The anti-A's and the anti-B's try to get through the placenta and they can't go. So it doesn't matter what the baby's blood cells look like when it comes to A and B antigens. So the baby could totally be rocking an A antigen. I know that the baby couldn't be rocking both A and B antigens, but that is a genetics question. And if the baby is rocking the RH antigen, this is where it gets sketchy. Mamas will not have anti-RHs unless they've been exposed to RH antigens in the past. Did you hear that? No antibodies unless exposed to RH antigens sometime in the past. If you follow what I just said, I know you cannot read that for the life of you. Who needs to read things? Baby number one, mama does not have any anti-RH antibodies. None. She doesn't have them in her blood. She's never been exposed to the RH antigen before. Push that baby out. Holy mixing of blood. Mom now gets exposed to the baby's RH factor. She's exposed to the RH factor. She builds anti-RHs because that thing should never come back. But guess what? That's baby number one. What happens to baby number two? Baby number two, these antibodies, run, run, run, run, run, run, run, run, run, run. They're like on a mission from the universe to come into baby number two and kick the holy living tar out of it. And it's true. It will kill you. Your anti-RH antibodies will kill your baby. It's a condition called erythroblastosis fatalis, fatalis fatalis dead baby. That's a sad story. So guess what you do? Take medicine to the rescue. Your doctors are going to make you take medicine to prevent the formation of anti-RH antibodies. One such medicine is called Rogam. And it prevents your immune system from producing those antibodies. As long as you don't ever produce them, you won't ever attack your baby. And you won't ever produce them unless you're exposed to the baby's blood. That's a good birth in any method. So really, the first baby is the only one that has a chance at survival if R-H factors don't match. If the R-H negative mama has an R-H positive baby. All right, why didn't AB bloods matter? Because the A and B antibodies can't cross the placenta. This is just like, hopefully that's review. So you're like, dude, I already learned that in Bio One. But I'm retelling you the story because I want you to start thinking about self, non-self, and have some context, some familiar context for grasping immune system madness, which is going to start in the next lecture. Bye, dog.