 I want to cover the four different types of immunity in this video, so let's cover the terminology first. So first we have natural versus artificial acquired. So natural acquired is something that would have happened as long as we've been a species. Artificially acquired is something that is done to you, right? It's a medical intervention. So natural versus artificial doesn't mean one's good and one's bad, but that's what the terms are. Then we have passive versus active. So passive is, again, something that's done to you or done for you, whereas active is something that your immune system has to do on its own. So let's go through each of the four categories. We'll just go in order here. So we have naturally acquired passive immunity first. This would be when, in a natural fashion, you are given antibodies from another source. So you see here your two options would be breast milk or through the placenta. IgG antibodies are the only antibodies of the five classes that cross through the placenta, but you are given your mom's IgG antibodies while you're in the womb. And then all five classes of antibodies are going to cross into breast milk. So a mother breastfeeding their child is an example of naturally acquired passive immunity. So babies don't really have a developed immune system, especially those first six months. And part of the reason why that hasn't been a problem across our evolutionary history is the fact that mom has loaned her immune system to the baby with breastfeeding. If it wasn't mom, it was a wet nurse or somebody. So mom was exposed to antigens. Mom made antibodies against those antigens, and then mom gave them to the baby. So that's one of the main benefits of breastfeeding is the fact that you're being given antibody therapy. So that's naturally acquired passive immunity. Next we have artificially acquired passive immunity. This is where you're given antibodies, but it's through a medical intervention. So antibodies are, like it says, they're harvested from a person or an animal and given to you. So think about in the movies, like the movie The Hot Zone, they have to get the antibodies from the monkey and give it to humans to save them. Or with the relatively recent Ebola outbreak, getting antibodies from someone that survived Ebola and giving them to people that have Ebola is a way to do that. So antibody therapies can be used in lots of situations. That would be where you're given someone else's antibodies, which is why it's passive immunity, but it's artificially acquired because it's something, it's a medical intervention. All right. So that is artificially acquired passive immunity. Next we have naturally acquired active immunity. This is where you're exposed to an antigen. You either got sick or you didn't. If you got sick and you didn't die, you would now have naturally acquired active immunity. So exposure to an antigen led to immunity. So you didn't have to get sick. We can get exposed to antigens, not get sick, but still recognize them and develop immunity against them. So that would be naturally acquired active immunity. Think I got sick, I didn't die, thankfully. And now I'm immune to that condition. So that's naturally acquired active immunity. Last one is artificially acquired active immunity. This would be vaccinations. So whereas antibody therapies give you the antibodies directly, vaccines expose you to the antigens, the cell fragments, the cell surface markers. Your immune system still has to do the work. So antibody therapy is directly going to go to work helping you fight off the infection. A vaccine is going to hang up wanted posters and tell your immune system what to look for, but your immune system still has to mount the response itself. So that is artificially acquired active immunity. So real quick review, naturally acquired passive immunity. Think breast milk or antibodies crossing the placenta. Naturally acquired passive immunity is antibody therapy. You directly give a human being antibodies to try to save them. Naturally acquired active immunity. You got sick, you didn't die, you recovered, and now you're immune. Artificially acquired active immunity. You get a vaccine, your body mounts an immune response to that pathogen without you having to have gotten sick and now you're immune. So those are the four types of immunity. Have a wonderful day. Be blessed.