WEBVTT - What Happens When Your Immune System Turns on You? 0:00:01.840 --> 0:00:08.639 Welcome to Brainstuff, a production of iHeartRadio. Hey Brainstuff Lauren Bogelbaum. Here, 0:00:10.480 --> 0:00:12.840 you might think of your body sort of like a 0:00:12.880 --> 0:00:16.759 fabulous estate with a lot of different departments and individual 0:00:16.800 --> 0:00:20.920 workers that keep the household running. For this metaphor, whether 0:00:21.000 --> 0:00:24.040 you want to imagine yourself as a medieval castle or 0:00:24.079 --> 0:00:27.720 a countryside manor, or more of a well staffed but 0:00:27.760 --> 0:00:32.120 nonetheless haunted mansion is up to you. You might say 0:00:32.159 --> 0:00:34.880 that you've got a kitchen staff in your digestive system, 0:00:34.920 --> 0:00:37.960 because it prepares nutrients for the whole household to use. 0:00:38.720 --> 0:00:41.320 Organs like your kidneys, are part of the cleaning staff. 0:00:42.479 --> 0:00:45.680 Your body also keeps a sharp security staff on hand 0:00:45.760 --> 0:00:48.760 in the form of your immune system. There are two 0:00:48.800 --> 0:00:52.800 subdepartments or branches within the immune system, the innate and 0:00:52.960 --> 0:00:56.440 the adaptive. A lot of germs that enter your body 0:00:56.480 --> 0:01:00.440 get dealt with with a swiftness by your innate immune system. 0:01:01.000 --> 0:01:04.160 This is a whole organization of defenses that keep out 0:01:04.200 --> 0:01:07.040 and kick out any sort of home invader at the home, 0:01:07.080 --> 0:01:11.080 in this case being you. Your innate immune system includes 0:01:11.080 --> 0:01:14.640 your skin and mucous membranes, which are physical barriers, and 0:01:14.760 --> 0:01:18.600 some cells and enzymes that scan for attack and kill 0:01:18.680 --> 0:01:21.280 any germs that do make it in of like in 0:01:21.319 --> 0:01:25.200 the state's physical walls and its camera network and security guards. 0:01:26.319 --> 0:01:29.919 The innate immune system is fairly automated and can't distinguish 0:01:29.959 --> 0:01:33.240 between different types of invaders that well, but it's really 0:01:33.280 --> 0:01:37.720 effective at stopping them before they make you sick. Unfortunately 0:01:37.760 --> 0:01:40.839 for us, some germs have evolved to evade our innate 0:01:40.880 --> 0:01:44.920 immune system. When for whatever reason, a germ survives in 0:01:44.959 --> 0:01:48.520 your body and keeps multiplying, the security guards of the 0:01:48.520 --> 0:01:52.400 innate immune system call into action that second branch, your 0:01:52.520 --> 0:01:57.400 adaptive immune system. It's called adaptive because it can learn 0:01:57.480 --> 0:02:02.800 about different germs and respond specific to each. It functions 0:02:02.920 --> 0:02:05.640 sort of like a network of live in detectives or 0:02:05.680 --> 0:02:08.680 special agents that build a database of all the germs 0:02:08.720 --> 0:02:12.160 they fought off over the course of your life. This 0:02:12.360 --> 0:02:15.480 is super cool because I mean, A, it keeps us alive, 0:02:15.760 --> 0:02:18.480 but B it also prevents us from getting sick from 0:02:18.520 --> 0:02:22.440 certain diseases twice like chicken pox. Once you've had it, 0:02:22.480 --> 0:02:26.359 you'll probably never get it again. The adaptive immune system 0:02:26.480 --> 0:02:29.919 is also why vaccines work. We can introduce a harmless 0:02:30.000 --> 0:02:32.200 version of a germ or bits of a germ to 0:02:32.320 --> 0:02:35.080 our adaptive immune system, and it'll learn how to recognize 0:02:35.080 --> 0:02:38.040 that germ, so should the real thing try to invade 0:02:38.080 --> 0:02:40.600 at a later time and date, your body can spring 0:02:40.639 --> 0:02:43.720 into action and fight it off quick You can see 0:02:43.760 --> 0:02:47.360 our whole episode on vaccines for more about that. The 0:02:47.360 --> 0:02:51.800 immune system and its two branches are hugely complex and interrelated. 0:02:52.360 --> 0:02:54.760 When it's all working correctly, it sets up a lot 0:02:54.760 --> 0:02:58.040 of checks and balances so that the cells, the workers 0:02:58.080 --> 0:03:01.680 within the system are aggressive about fighting off invaders, but 0:03:01.880 --> 0:03:05.040 also don't make mistakes in the form of friendly fire 0:03:05.320 --> 0:03:10.280 or too much collateral damage. But because of that complexity, 0:03:10.440 --> 0:03:14.520 there's also a lot of things that can go wrong. Today, 0:03:14.680 --> 0:03:17.400 let's talk more about how your adaptive immune system works 0:03:17.520 --> 0:03:21.880 and what can happen when it turns against you. The 0:03:22.040 --> 0:03:25.680 primary workers in your adaptive immune system, your detectives or 0:03:25.720 --> 0:03:30.880 special agents, are a category of cells called lymphocytes. They're 0:03:30.919 --> 0:03:33.920 called that because when they're not actively fighting off an infection, 0:03:34.200 --> 0:03:38.680 they mostly hang out dormant in your lymph nodes. These 0:03:38.680 --> 0:03:41.440 are small organs that you have many of throughout your body, 0:03:41.800 --> 0:03:44.000 though you might be most familiar with the two in 0:03:44.040 --> 0:03:47.720 your upper neck on either side of your windpipe. You 0:03:47.840 --> 0:03:50.280 might have had a doctor or parent feel for those 0:03:50.320 --> 0:03:53.800 when you've had a cold, because during an infection, they're 0:03:53.840 --> 0:03:57.240 a base of operations for lymphocytes, so if you're fighting 0:03:57.280 --> 0:04:00.920 something off, they tend to swell up. There are two 0:04:01.040 --> 0:04:05.840 categories of lymphocytes, B cells and T cells. T cells 0:04:05.840 --> 0:04:08.520 are called that because they mature in the thymus after 0:04:08.560 --> 0:04:11.600 having been created in your bone marrow. B cells are 0:04:11.640 --> 0:04:14.360 created and mature in the bone marrow, which is why 0:04:14.360 --> 0:04:17.839 they're called B cells. That's not super important, but I 0:04:18.000 --> 0:04:20.480 just learned that, and I had always wondered about the names, 0:04:20.520 --> 0:04:24.840 so I thought i'd share. Anyway, In their downtime, your 0:04:24.920 --> 0:04:29.360 lymphocytes are mostly hanging out in their headquarters, your lymph nodes, 0:04:29.600 --> 0:04:33.920 waiting for a call to action. When your innate immune 0:04:33.960 --> 0:04:39.040 system encounters germs, specialized security guard cells come to lymph 0:04:39.080 --> 0:04:43.920 nodes to tell the lymphocytes about it. What's technically happening 0:04:44.000 --> 0:04:46.720 is that the innate immune cell eats the germ and 0:04:46.800 --> 0:04:49.240 breaks it apart and displays bits of the germ on 0:04:49.320 --> 0:04:53.039 its surface. But that gets real grizzly for our metaphor, 0:04:53.320 --> 0:04:56.520 So let's say it's like showing some security cam footage. 0:04:57.960 --> 0:05:02.720 These germ bits or identic buying footage are what's called antigens. 0:05:03.760 --> 0:05:06.640 We've talked about antigens on the show before. There are 0:05:06.640 --> 0:05:10.440 molecules that occur on the surface of germs and cells 0:05:10.560 --> 0:05:13.680 and other stuff that your immune system can use to 0:05:13.880 --> 0:05:18.240 id whatever it is. If the thing in question is 0:05:18.279 --> 0:05:21.520 from your own body and thus belongs there, your immune 0:05:21.520 --> 0:05:25.719 system should recognize that. If it's not, your adaptive immune 0:05:25.720 --> 0:05:29.719 system's job is to create a specific attack against germs 0:05:29.839 --> 0:05:34.560 bearing that antigen and then remember it later. Here's how 0:05:34.600 --> 0:05:37.640 it works. The T cells in your lymph nodes can 0:05:37.880 --> 0:05:41.599 test a presented antigen and see whether they recognize it 0:05:41.640 --> 0:05:43.600 because your body has fought a germ with it before. 0:05:44.839 --> 0:05:49.160 Each individual T cell tests for, or recognizes, or fits 0:05:49.200 --> 0:05:52.320 to a single antigen like a key in a lock. 0:05:53.520 --> 0:05:55.960 Even if it's a new to you antigen, that's okay. 0:05:56.200 --> 0:05:58.440 Eventually your system will find a T cell that fits 0:05:58.480 --> 0:06:02.640 well enough as a remembered antigen. That's great. The whole process 0:06:02.680 --> 0:06:06.400 can go quicker. When a T cell fits to an antigen, 0:06:06.680 --> 0:06:10.039 it activates a response like a red alert. The T 0:06:10.200 --> 0:06:13.760 cells starts to replicate rapidly, producing copies of itself that 0:06:13.800 --> 0:06:18.120 are all custom fitted to that particular antigen. This is 0:06:18.200 --> 0:06:21.000 really helpful because T cells are sort of like your 0:06:21.000 --> 0:06:25.520 body's targeted assassins. They seek out and attack germs and 0:06:25.640 --> 0:06:30.240 infected cells directly based on the particular antigen that they recognize. 0:06:31.480 --> 0:06:35.000 T cells can also chemically signal other immune cells to 0:06:35.200 --> 0:06:39.840 come help and can help activate your B cells. B 0:06:39.960 --> 0:06:43.839 cells are sort of like your weapons experts. They create 0:06:43.880 --> 0:06:49.160 what's called antibodies. Antibodies are specific proteins that your body 0:06:49.200 --> 0:06:54.159 builds to match specific antigens. Antibodies can bind to their 0:06:54.200 --> 0:06:57.200 matching antigen on the surface of a germ, rendering the 0:06:57.240 --> 0:07:00.640 germ unable to do any harm, and also serve to 0:07:00.800 --> 0:07:04.480 flag that germ or a germ infected cell for destruction. 0:07:05.880 --> 0:07:09.039 At this point in the estate metaphor, I'm not sure 0:07:09.080 --> 0:07:12.160 exactly what kind of household we're running here, maybe a 0:07:12.280 --> 0:07:17.760 supervillain's compound, but let's just roll with it. So, after 0:07:17.800 --> 0:07:21.400 your immune system has cleared an infection, it will stockpile 0:07:21.560 --> 0:07:24.840 that particular antibody and keep around some T cells that 0:07:24.920 --> 0:07:30.960 recognize that antigen in most cases forever. So if your 0:07:30.960 --> 0:07:33.920 immune system encounters antigens of the same type later on 0:07:34.440 --> 0:07:38.520 Bada bing Bada boom, where Bada bing boda boom indicates 0:07:38.560 --> 0:07:43.000 that networks within networks of intracellular communication and coordinated efforts 0:07:43.080 --> 0:07:48.920 will occur. It's all again really complex, which means a 0:07:48.960 --> 0:07:53.640 lot of different things can go wrong. For example, not 0:07:53.920 --> 0:07:57.320 everything that your immune system IDs using antigens as not 0:07:57.520 --> 0:08:02.440 self and thus potentially unsafe, is actually a threat. This 0:08:02.480 --> 0:08:05.120 is how we wind up with allergies to not just 0:08:05.240 --> 0:08:10.560 harmless but actively adorable things like cats and flowers. For 0:08:10.640 --> 0:08:13.480 some reason, your immune system looks at a granule of 0:08:13.520 --> 0:08:16.520 pollen or pet dander and tries to clear it out 0:08:16.560 --> 0:08:19.240 of your body with the same kind of extreme prejudice 0:08:19.240 --> 0:08:23.040 it would a disease causing germ. Your innate immune system 0:08:23.040 --> 0:08:26.200 triggers lots of inflammation to help get fighting resources to 0:08:26.240 --> 0:08:29.960 the area, say your nose, but there's really nothing to fight, 0:08:30.360 --> 0:08:34.840 so you just wind up swollen and itchy. There are 0:08:34.880 --> 0:08:37.960 also some types of germs that actively mess with your 0:08:38.000 --> 0:08:42.840 immune system. That's what originally made the human immuno deficiency 0:08:42.920 --> 0:08:48.000 viruses or HIV so scary. HIV infects and kills immune 0:08:48.000 --> 0:08:52.240 system cells like T cells in order to spread. There 0:08:52.280 --> 0:08:55.280 have been some amazing advances in treating and preventing HIV 0:08:55.360 --> 0:08:58.040 in recent years. It's very manageable. Now I'll have to 0:08:58.040 --> 0:09:02.040 do a whole episode about it. Anyway. There are also 0:09:02.320 --> 0:09:05.240 a number of conditions that happen when the adaptive immune 0:09:05.240 --> 0:09:10.760 system starts confusing your own cells for invaders. Every cell 0:09:10.800 --> 0:09:13.520 in our bodies should be coded as self thanks to 0:09:13.600 --> 0:09:17.120 antigens on the cell's surface. It's sort of like wearing 0:09:17.120 --> 0:09:20.840 an id. Bad antigens tell your immune system at a glance, 0:09:21.120 --> 0:09:25.400 hey I'm cool, I work here. There are entire processes 0:09:25.400 --> 0:09:28.480 in your body to curate your T cells and B cells, 0:09:28.520 --> 0:09:31.080 but keep their activity in check and make sure that 0:09:31.160 --> 0:09:34.120 ones that seem to want to attack self codd cells 0:09:34.440 --> 0:09:38.160 don't get into circulation in the first place. But it 0:09:38.280 --> 0:09:43.319 still happens, and this category of conditions is called autoimmune disorders. 0:09:44.360 --> 0:09:47.880 It includes things like arthritis, in which your immune system 0:09:47.920 --> 0:09:51.720 attacks your joints, type one diabetes in which it attacks 0:09:51.720 --> 0:09:57.280 your pancreas, multiple sclerosis which damages nerve cells, and psoriasis, 0:09:57.320 --> 0:10:01.439 which damages the skin leading to scaly, pass or other problems. 0:10:02.480 --> 0:10:06.160 Autoimmune disorders tend to be frustrating to treat, after all, 0:10:06.240 --> 0:10:09.560 You can't just remove and replace a malfunctioning immune system 0:10:09.760 --> 0:10:14.280 the way you might a kidney. Also, we don't understand 0:10:14.320 --> 0:10:19.360 exactly why any given autoimmune disorder happens. There is a 0:10:19.440 --> 0:10:21.720 lot of research going into this, and we've got a 0:10:21.760 --> 0:10:25.280 lot of good starting concepts, but again, the entire immune 0:10:25.280 --> 0:10:28.040 process is so complex that it's hard to nail things down. 0:10:29.400 --> 0:10:33.360 For example, researchers have identified sets of genes that code 0:10:33.400 --> 0:10:37.360 for things like how your immune cells recognize antigens or 0:10:37.679 --> 0:10:41.880 how your body's cells produce their self ID. It makes 0:10:41.920 --> 0:10:44.800 sense that errors in this coding could lead to problems. 0:10:46.000 --> 0:10:49.160 Other research has looked into malfunctions in T cells that 0:10:49.360 --> 0:10:52.800 lead them to overproduce those signal molecules that call in 0:10:52.840 --> 0:10:56.240 the troops, which also leads to inflammation, which tends to 0:10:56.320 --> 0:11:00.520 be an issue in autoimmune disorders. Yet other research is 0:11:00.600 --> 0:11:03.480 diving in two malfunctions in a subset of T cells 0:11:03.600 --> 0:11:07.400 called regulatory T cells, that are supposed to regulate their 0:11:07.440 --> 0:11:10.360 fellow workers in the immune system, shutting down the red 0:11:10.400 --> 0:11:15.559 alert after an infection has been cleared, and suppressing excess activity. 0:11:15.640 --> 0:11:17.880 Even when we do have a decent idea of what's 0:11:17.920 --> 0:11:21.480 going wrong, immune disorders of all types can be difficult 0:11:21.559 --> 0:11:26.120 to treat, but there are increasingly effective therapies that can 0:11:26.200 --> 0:11:30.640 ease symptoms or even target particular immune system activities to 0:11:30.679 --> 0:11:34.640 help bring it back closer to normal. As always, if 0:11:34.720 --> 0:11:38.559 you or a loved one is experiencing strange inflammation or 0:11:38.600 --> 0:11:42.640 other irritating or painful symptoms with no obvious cause. You 0:11:42.720 --> 0:11:46.360 know you didn't stub your skin, definitely get in touch 0:11:46.440 --> 0:11:49.320 with a healthcare professional. They'll be able to help you 0:11:49.320 --> 0:11:52.840 get a diagnosis and a treatment plan, even if your 0:11:52.880 --> 0:11:56.120 body is a supervillain's layer that may or may not 0:11:56.320 --> 0:12:03.640 be haunted. Today's episode is an original written by me. 0:12:04.240 --> 0:12:06.520 Brain Stuff is production of iHeart Radio and is produced 0:12:06.520 --> 0:12:09.880 by Tyler Klang. Four more podcasts from iHeartRadio visit the 0:12:09.920 --> 0:12:13.160 iHeartRadio app, Apple Podcasts, or wherever you listen to your 0:12:13.160 --> 0:12:13.920 favorite shows.