# Immune  ## Metadata - Author: [[Philipp Dettmer]] - Full Title: Immune - Category: #books ## Highlights - At its very core, the immune system is a tool to distinguish the other from the self. It does not matter if the other means to harm you or not. If the other is not on a very exclusive guest list that grants free passage, it has to be attacked and destroyed because the other might harm you. In the world of the immune system, any “other” is not a risk worth taking. Without this commitment you would die within days. And as we will learn later, sadly, when your immune system under- or overcommits, death or suffering are the consequences. While identifying what is self and what is other is the core, it is not technically the goal of your immune system. The goal above all things is maintaining and establishing homeostasis: the equilibrium between all the elements and cells in the body. ([Location 270](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=270)) ## New highlights added May 12, 2024 at 11:01 PM - Something alive separates itself from the universe around it. It has a metabolism, meaning it takes up nutrients from the outside and gets rid of internal garbage. It responds to stimuli. It grows and it can make more of itself. ([Location 413](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=413)) - Tags: [[orange]] - Cells are filled up by proteins. Proteins are three-dimensional puzzle pieces. Their specific shapes enable them to fit together or interact with other proteins in specific ways. Sequences of these interactions, called pathways, cause cells to do things. This is what we mean when we say that cells are protein robots guided by biochemistry. The complex interactions between dumb and dead proteins create a less dumb and less dead cell, and the complex interactions between slightly dumb cells create the pretty smart immune system. ([Location 507](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=507)) - Tags: [[orange]] - According to pretty new science, chronic inflammation is involved in more than half of all deaths each year as it is an underlying cause of a wide variety of diseases—from various cancers to strokes or liver failure. And yes, you read that correctly—for at least one in two people who died today, chronic inflammation was the underlying cause of the disease that killed them. ([Location 1040](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1040)) - Tags: [[orange]] - In a nutshell, inflammation is a process that makes the cells in blood vessels change their shape, so that plasma, the liquid part from your blood, can flood into a wounded or infected tissue. You can literally imagine this as floodgates opening and a tsunami of water, filled with salts and all sorts of special attack proteins, flooding the spaces between your cells so rapidly that tissue on the scale of a metropolitan area balloons up. ([Location 1045](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1045)) - Tags: [[orange]] - If you hurt yourself and tissue is destroyed and they die or they get really agitated, Mast Cells release their inflammation supercharger chemicals and speed up the process immensely. This way the tissue below your skin has an inflammation emergency button. ([Location 1079](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1079)) - Tags: [[orange]] - So to summarize the important parts: Cells have millions of noses on their outsides that are called receptors. They communicate by releasing proteins that carry information, called cytokines. When a cell smells cytokines with their receptors (noses), they trigger pathways inside the cell that change their gene expression and therefore the behavior of the cell. So cells can react to information without being conscious or having the ability to think, guided by the biochemistry of life. This enables them to do pretty smart things even though they are technically very stupid. Some cytokines do also function as a navigation system—an immune cell can smell where they are coming from and literally follow their noses to the battlefield. ([Location 1188](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1188)) - Tags: [[orange]] - Basically the complement system is an army of over thirty different proteins (not cells!) that work together in an elegant dance to stop strangers from having a good time inside your body. ([Location 1302](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1302)) - Tags: [[orange]] - Your network of lymphatic vessels is miles long and covers your entire body. It is a sort of partner system to your blood vessels and blood. The main job of your blood is to carry resources like oxygen to every cell in the body and to do that, some of the blood needs to actually leave your blood vessels and drain into your tissue and organs to deliver the goods directly to your cells. (Which makes total sense if you think about it for a moment but still feels a bit weird.) Most of that blood is then reabsorbed by your blood vessels. But some of its liquid parts remain in the tissue between your cells and need to be transported back into circulation again. The lymphatic system is responsible for this job. It sort of constantly drains your body and tissues of excess fluid and delivers it back to the blood where it can circulate again—if it didn’t, you would swell up like a balloon over time. ([Location 1469](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1469)) - Tags: [[orange]] - The answer is as simple as it is baffling: The immune system does not so much adapt to new invaders as it already was adapted when you were born. It comes preinstalled with hundreds of millions of different immune cells—a few for every possible threat that you could possibly encounter in this universe. Right now you have at least one cell inside you that is a specific weapon against the Black Death, any variant of the flu, the coronavirus, and the first pathogenic bacteria that will emerge in a city on Mars in one hundred years. You are ready for every possible microorganism in this universe. ([Location 1628](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1628)) - Tags: [[orange]] - For every possible antigen that is possible in the universe, you have the potential to recognize it inside you right now. ([Location 1652](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1652)) - Tags: [[orange]] - In principle, this is what your adaptive immune cells do with gene fragments. It takes gene segments and randomly combines them, then it does the same again, and then it randomly pulls out or adds in parts, to create billions of different receptors. They have three different groups of gene fragments. They randomly choose one from each group and put them together. This is the main course. Then they do this again, but with fewer fragments for the dessert. And then when they are done, they randomly remove or add in parts. This way your adaptive immune cells create at least hundreds of millions of unique receptors. Each of them fitting one possible guest at the dinner party, which in this case is an antigen from a microorganism that could invade your body. ([Location 1693](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1693)) - Tags: [[orange]] - So in the final exam the T Cells are presented with all sorts of protein combinations that are used by the cells of your body. The way this happens is pretty fascinating by the way—the teacher cells in the Thymus that do the testing have a special license to make all sorts of special proteins that usually are made only in organs like the heart, pancreas, or the liver and also hormones, like insulin for example. This way they can show the T Cell all kinds of proteins that are marked as “self.” If a T Cell is able to recognize any of these self-proteins, they are taken out back and shot in the head immediately.*3 ([Location 1746](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1746)) - Tags: [[orange]] - The Dendritic Cell is an antigen-presenting cell, which is a complicated way of saying: “covering yourself in your enemies’ guts.” ([Location 1814](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1814)) - Tags: [[orange]] - Let us summarize one last time because this stuff is really important and really hard: To activate your Adaptive Immune System, a Dendritic Cell needs to kill enemies and rip them into pieces called antigens, which you can imagine as wieners. These antigens are put into special molecules, called MHC class II molecules, that you can imagine like hot dog buns. On the other end, Helper T Cells rearrange gene segments to create a single specific receptor that is able to connect to one specific antigen (a specific wiener). The Dendritic Cell is looking for just the right Helper T Cell that can bind its specific receptor to the antigen. And if a matching T Cell is found the two cells interlock. But then there needs to be a second signal, like a gentle encouraging kiss on the cheek, that tells the T Cell that all is good and the signal from the presented antigen is real. And only then does a Helper T Cell activate. ([Location 1851](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=1851)) - Tags: [[orange]] ## New highlights added May 21, 2024 at 7:48 AM - We mentioned before that the Innate Immune System is responsible for activating and providing context to the Adaptive Immune System and here we are encountering this principle once more! ([Location 2065](https://readwise.io/to_kindle?action=open&asin=B08XTNHRR5&location=2065)) - Tags: [[orange]]