Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff Lauren Bogelbaum. Here, you might think of your body sort of like a fabulous estate with a lot of different departments and individual workers that keep the household running. For this metaphor, whether you want to imagine yourself as a medieval castle or a countryside manor, or more of a well staffed but
nonetheless haunted mansion is up to you. You might say that you've got a kitchen staff in your digestive system, because it prepares nutrients for the whole household to use. Organs like your kidneys, are part of the cleaning staff. Your body also keeps a sharp security staff on hand in the form of your immune system. There are two subdepartments or branches within the immune system, the innate and
the adaptive. A lot of germs that enter your body get dealt with with a swiftness by your innate immune system. This is a whole organization of defenses that keep out and kick out any sort of home invader at the home,
in this case being you. Your innate immune system includes your skin and mucous membranes, which are physical barriers, and some cells and enzymes that scan for attack and kill any germs that do make it in of like in the state's physical walls and its camera network and security guards. The innate immune system is fairly automated and can't distinguish between different types of invaders that well, but it's really
effective at stopping them before they make you sick. Unfortunately for us, some germs have evolved to evade our innate immune system. When for whatever reason, a germ survives in your body and keeps multiplying, the security guards of the innate immune system call into action that second branch, your adaptive immune system. It's called adaptive because it can learn
about different germs and respond specific to each. It functions sort of like a network of live in detectives or special agents that build a database of all the germs they fought off over the course of your life. This is super cool because I mean, A, it keeps us alive, but B it also prevents us from getting sick from certain diseases twice like chicken pox. Once you've had it, you'll probably never get it again. The adaptive immune system
is also why vaccines work. We can introduce a harmless version of a germ or bits of a germ to our adaptive immune system, and it'll learn how to recognize that germ, so should the real thing try to invade at a later time and date, your body can spring into action and fight it off quick You can see our whole episode on vaccines for more about that. The immune system and its two branches are hugely complex and interrelated.
When it's all working correctly, it sets up a lot of checks and balances so that the cells, the workers within the system are aggressive about fighting off invaders, but also don't make mistakes in the form of friendly fire or too much collateral damage. But because of that complexity, there's also a lot of things that can go wrong. Today, let's talk more about how your adaptive immune system works
and what can happen when it turns against you. The primary workers in your adaptive immune system, your detectives or special agents, are a category of cells called lymphocytes. They're called that because when they're not actively fighting off an infection, they mostly hang out dormant in your lymph nodes. These are small organs that you have many of throughout your body, though you might be most familiar with the two in
your upper neck on either side of your windpipe. You might have had a doctor or parent feel for those when you've had a cold, because during an infection, they're a base of operations for lymphocytes, so if you're fighting something off, they tend to swell up. There are two categories of lymphocytes, B cells and T cells. T cells are called that because they mature in the thymus after having been created in your bone marrow. B cells are created and mature in the bone marrow, which is why
they're called B cells. That's not super important, but I just learned that, and I had always wondered about the names, so I thought i'd share. Anyway, In their downtime, your lymphocytes are mostly hanging out in their headquarters, your lymph nodes, waiting for a call to action. When your innate immune system encounters germs, specialized security guard cells come to lymph
nodes to tell the lymphocytes about it. What's technically happening is that the innate immune cell eats the germ and breaks it apart and displays bits of the germ on its surface. But that gets real grizzly for our metaphor, So let's say it's like showing some security cam footage. These germ bits or identic buying footage are what's called antigens.
We've talked about antigens on the show before. There are molecules that occur on the surface of germs and cells and other stuff that your immune system can use to id whatever it is. If the thing in question is from your own body and thus belongs there, your immune system should recognize that. If it's not, your adaptive immune system's job is to create a specific attack against germs bearing that antigen and then remember it later. Here's how
it works. The T cells in your lymph nodes can test a presented antigen and see whether they recognize it because your body has fought a germ with it before. Each individual T cell tests for, or recognizes, or fits to a single antigen like a key in a lock. Even if it's a new to you antigen, that's okay. Eventually your system will find a T cell that fits well enough as a remembered antigen. That's great. The whole process can go quicker. When a T cell fits to an antigen,
it activates a response like a red alert. The T cells starts to replicate rapidly, producing copies of itself that are all custom fitted to that particular antigen. This is really helpful because T cells are sort of like your body's targeted assassins. They seek out and attack germs and infected cells directly based on the particular antigen that they recognize. T cells can also chemically signal other immune cells to come help and can help activate your B cells. B
cells are sort of like your weapons experts. They create what's called antibodies. Antibodies are specific proteins that your body builds to match specific antigens. Antibodies can bind to their matching antigen on the surface of a germ, rendering the germ unable to do any harm, and also serve to flag that germ or a germ infected cell for destruction. At this point in the estate metaphor, I'm not sure exactly what kind of household we're running here, maybe a
supervillain's compound, but let's just roll with it. So, after your immune system has cleared an infection, it will stockpile that particular antibody and keep around some T cells that recognize that antigen in most cases forever. So if your immune system encounters antigens of the same type later on Bada bing Bada boom, where Bada bing boda boom indicates that networks within networks of intracellular communication and coordinated efforts
will occur. It's all again really complex, which means a lot of different things can go wrong. For example, not everything that your immune system IDs using antigens as not self and thus potentially unsafe, is actually a threat. This is how we wind up with allergies to not just harmless but actively adorable things like cats and flowers. For some reason, your immune system looks at a granule of pollen or pet dander and tries to clear it out of your body with the same kind of extreme prejudice
it would a disease causing germ. Your innate immune system triggers lots of inflammation to help get fighting resources to the area, say your nose, but there's really nothing to fight, so you just wind up swollen and itchy. There are also some types of germs that actively mess with your immune system. That's what originally made the human immuno deficiency viruses or HIV so scary. HIV infects and kills immune
system cells like T cells in order to spread. There have been some amazing advances in treating and preventing HIV in recent years. It's very manageable. Now I'll have to do a whole episode about it. Anyway. There are also a number of conditions that happen when the adaptive immune system starts confusing your own cells for invaders. Every cell in our bodies should be coded as self thanks to antigens on the cell's surface. It's sort of like wearing
an id. Bad antigens tell your immune system at a glance, hey I'm cool, I work here. There are entire processes in your body to curate your T cells and B cells, but keep their activity in check and make sure that ones that seem to want to attack self codd cells don't get into circulation in the first place. But it still happens, and this category of conditions is called autoimmune disorders.
It includes things like arthritis, in which your immune system attacks your joints, type one diabetes in which it attacks your pancreas, multiple sclerosis which damages nerve cells, and psoriasis, which damages the skin leading to scaly, pass or other problems. Autoimmune disorders tend to be frustrating to treat, after all, You can't just remove and replace a malfunctioning immune system the way you might a kidney. Also, we don't understand
exactly why any given autoimmune disorder happens. There is a lot of research going into this, and we've got a lot of good starting concepts, but again, the entire immune process is so complex that it's hard to nail things down. For example, researchers have identified sets of genes that code for things like how your immune cells recognize antigens or how your body's cells produce their self ID. It makes sense that errors in this coding could lead to problems.
Other research has looked into malfunctions in T cells that lead them to overproduce those signal molecules that call in the troops, which also leads to inflammation, which tends to be an issue in autoimmune disorders. Yet other research is diving in two malfunctions in a subset of T cells called regulatory T cells, that are supposed to regulate their fellow workers in the immune system, shutting down the red alert after an infection has been cleared, and suppressing excess activity.
Even when we do have a decent idea of what's going wrong, immune disorders of all types can be difficult to treat, but there are increasingly effective therapies that can ease symptoms or even target particular immune system activities to help bring it back closer to normal. As always, if you or a loved one is experiencing strange inflammation or other irritating or painful symptoms with no obvious cause. You know you didn't stub your skin, definitely get in touch
with a healthcare professional. They'll be able to help you get a diagnosis and a treatment plan, even if your body is a supervillain's layer that may or may not be haunted. Today's episode is an original written by me. Brain Stuff is production of iHeart Radio and is produced by Tyler Klang. Four more podcasts from iHeartRadio visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.