1 00:00:11,678 --> 00:00:13,513 [Melanie] No environment is static over time. 2 00:00:14,431 --> 00:00:15,682 The climate will change. 3 00:00:15,765 --> 00:00:18,810 The composition of organisms living in that environment will change. 4 00:00:21,896 --> 00:00:26,276 [narrator] As a species, we've endured massive changes in our surroundings. 5 00:00:26,359 --> 00:00:27,902 Cataclysmic shifts. 6 00:00:28,528 --> 00:00:32,198 Our greatest challenge has always been adapting. 7 00:00:37,078 --> 00:00:40,749 And that means constantly defending against all of the threats we face 8 00:00:40,832 --> 00:00:42,834 in the organisms that live among us. 9 00:00:46,671 --> 00:00:50,759 The immune system, essential to our survival every second, 10 00:00:50,842 --> 00:00:55,138 is the most complex and least understood piece of our biology. 11 00:00:55,805 --> 00:00:58,224 And that's because it's always changing. 12 00:00:59,309 --> 00:01:00,769 As new enemies crop up… 13 00:01:02,687 --> 00:01:04,481 this system meets the challenge… 14 00:01:07,108 --> 00:01:08,526 and is transformed. 15 00:01:09,152 --> 00:01:12,822 The immune system is basically our body's defense system 16 00:01:12,906 --> 00:01:15,158 against all things foreign. 17 00:01:18,578 --> 00:01:22,290 Not only is our immune system effective at killing, 18 00:01:22,373 --> 00:01:25,877 it's also really effective at communication, memory, 19 00:01:25,960 --> 00:01:28,505 tagging other cells when it needs the help. 20 00:01:29,172 --> 00:01:30,924 It's a huge specialized army. 21 00:01:32,509 --> 00:01:35,386 [narrator] And to the naked eye, it's invisible. 22 00:01:38,014 --> 00:01:41,017 Unlike other systems, where we can point to a center, 23 00:01:41,101 --> 00:01:42,811 like the heart or the brain, 24 00:01:42,894 --> 00:01:47,107 the immune system is unique in that it lives everywhere, 25 00:01:47,190 --> 00:01:49,234 and it is always on the move. 26 00:01:51,361 --> 00:01:52,946 [energetic music playing] 27 00:02:16,719 --> 00:02:19,139 [Cat Bigney] Survival out here is extreme. 28 00:02:24,018 --> 00:02:27,272 There are days when I feel like I'm floating across the landscape, 29 00:02:27,355 --> 00:02:29,023 when everything is beautiful. 30 00:02:30,608 --> 00:02:33,611 And then there are other days, where I'm totally wrecked, 31 00:02:34,404 --> 00:02:36,865 exhausted, dehydrated, 32 00:02:37,574 --> 00:02:39,200 very sleep-deprived. 33 00:02:40,827 --> 00:02:45,331 I know full well that at any point in time, I could die here. 34 00:02:50,170 --> 00:02:52,005 My name is Cat Bigney, 35 00:02:52,088 --> 00:02:57,677 and I've been teaching and consulting in the wilderness for over two decades. 36 00:02:59,804 --> 00:03:01,639 In many ways, this is my home. 37 00:03:09,230 --> 00:03:11,733 At times I'll spend months out here, 38 00:03:13,568 --> 00:03:16,446 with very limited contact with the outside world. 39 00:03:17,989 --> 00:03:22,535 To survive in this environment requires a lot of awareness 40 00:03:22,619 --> 00:03:25,413 and the ability to embrace hardship and discomfort. 41 00:03:26,414 --> 00:03:27,248 Ouch! 42 00:03:30,168 --> 00:03:33,463 Every time I'm out, I end up having some sort of cut or abrasion, 43 00:03:34,005 --> 00:03:35,882 cactus spines in my hands and feet. 44 00:03:35,965 --> 00:03:37,217 It's just part of it. 45 00:03:39,886 --> 00:03:41,429 [narrator] On a microscopic level, 46 00:03:41,512 --> 00:03:44,849 our bodies are in a constant struggle with the environment. 47 00:03:46,226 --> 00:03:49,729 And the immune system manages every second of that struggle. 48 00:03:53,066 --> 00:03:56,277 [Nina Tandon] Our skin has cells that are very specialized 49 00:03:56,361 --> 00:03:58,446 to create a boundary between us 50 00:03:58,529 --> 00:03:59,989 and the outside world. 51 00:04:01,074 --> 00:04:04,160 [narrator] Imagine you're in the midday desert heat. 52 00:04:05,662 --> 00:04:08,498 You're walking on hot, loose rocks. 53 00:04:10,124 --> 00:04:12,835 What are you relying on most to stay alive? 54 00:04:14,754 --> 00:04:16,130 It's your biggest organ. 55 00:04:16,798 --> 00:04:20,260 And it also happens to be the bedrock of the immune system. 56 00:04:22,971 --> 00:04:23,805 Skin. 57 00:04:24,430 --> 00:04:27,517 From the moment we are born, 58 00:04:27,600 --> 00:04:32,730 we are exposed to the external environment and the sun's rays, 59 00:04:32,814 --> 00:04:37,568 but also the extraordinarily complex environment 60 00:04:37,652 --> 00:04:40,196 that's generated from our own body's inner workings. 61 00:04:43,866 --> 00:04:47,578 [narrator] The outermost layer of our skin  is like a brick wall 62 00:04:48,413 --> 00:04:49,539 that can breathe. 63 00:04:50,957 --> 00:04:54,002 It's made up of cells that bind tightly together 64 00:04:54,085 --> 00:04:57,130 to keep out UV rays and foreign objects. 65 00:04:58,214 --> 00:05:02,176 And the oil that sits on top of these cells is antibacterial. 66 00:05:02,802 --> 00:05:04,637 Another first line of defense. 67 00:05:05,513 --> 00:05:08,891 And in our 20 or so square feet of skin 68 00:05:08,975 --> 00:05:13,479 are tens of millions of immune cells that activate when there's a threat. 69 00:05:16,983 --> 00:05:19,402 But as tight a barrier as it is, 70 00:05:19,485 --> 00:05:23,614 occasionally something does end up slipping through this top layer. 71 00:05:24,824 --> 00:05:29,579 Microscopic bugs, or microbes, can hitch a ride in on almost anything. 72 00:05:32,123 --> 00:05:34,959 When they do, there's an immediate reaction. 73 00:05:37,420 --> 00:05:39,672 [Alok Patel] On the outside of microbes, 74 00:05:40,298 --> 00:05:42,967 there are these little molecules, called antigens. 75 00:05:43,051 --> 00:05:47,847 Our immune system is specifically trained to recognize foreign antigen, 76 00:05:47,930 --> 00:05:50,683 friendly antigen, and if it recognizes foreign, 77 00:05:50,767 --> 00:05:52,769 that's when the cascaded offense starts. 78 00:05:55,355 --> 00:05:58,316 [narrator] Below that top layer of skin is another one. 79 00:05:59,901 --> 00:06:01,444 Twenty times thicker. 80 00:06:03,946 --> 00:06:06,366 When something foreign gets down deep enough, 81 00:06:06,449 --> 00:06:08,659 the immune cells sense it immediately. 82 00:06:09,535 --> 00:06:11,329 They send a signal inside the body. 83 00:06:11,913 --> 00:06:14,707 Blood will rush to the damaged area. 84 00:06:14,791 --> 00:06:16,959 White blood cells, called neutrophils, 85 00:06:17,043 --> 00:06:21,339 will swarm in and kill the microbes by eating them. 86 00:06:29,931 --> 00:06:33,684 To us, inflammation might seem like a bad thing. 87 00:06:33,768 --> 00:06:38,106 But, really, it's just proof that the immune cells are doing their job. 88 00:06:41,401 --> 00:06:44,862 [Cat] I trust that my body can handle superficial infections out here. 89 00:06:44,946 --> 00:06:47,532 The desert environment is forgiving in some ways 90 00:06:47,615 --> 00:06:49,325 because it's so arid and dry. 91 00:06:49,409 --> 00:06:50,993 It is somewhat sterile. 92 00:06:51,077 --> 00:06:52,995 So, if I have a scratch in the desert, 93 00:06:53,079 --> 00:06:55,623 my body will naturally be able to fight that off 94 00:06:55,706 --> 00:06:57,750 better than if I were in a jungle environment. 95 00:07:00,336 --> 00:07:02,839 [narrator] After the infection has been brought under control, 96 00:07:02,922 --> 00:07:07,427 the body then has to repair the spot where the microbe got through. 97 00:07:08,553 --> 00:07:12,265 [Nina] Our bodies have this innate capacity to repair, 98 00:07:12,348 --> 00:07:15,518 and some of our tissues repair themselves more than others. 99 00:07:15,601 --> 00:07:19,897 Like skin, for example, is constantly regenerating. 100 00:07:21,023 --> 00:07:22,567 [narrator] Even without a breach, 101 00:07:22,650 --> 00:07:28,573 we shed about 40,000 skin cells a minute or 50 million every day. 102 00:07:29,365 --> 00:07:31,325 So, when a wound heals, 103 00:07:31,409 --> 00:07:34,328 that outer layer of cells dies and falls off. 104 00:07:34,412 --> 00:07:38,708 But beneath them are cells that constantly replenish the skin above it, 105 00:07:39,292 --> 00:07:41,836 and those new cells have a memory. 106 00:07:42,670 --> 00:07:45,840 Inflammation from damage sensitizes those cells, 107 00:07:45,923 --> 00:07:50,386 so the next time around, they actually respond faster. 108 00:07:50,470 --> 00:07:55,099 Skin, it turns out, that's been roughed up before, can heal twice as fast. 109 00:07:58,060 --> 00:08:00,688 So, after decades of cactus thorns, 110 00:08:01,689 --> 00:08:05,443 Cat's primary defenses are way tougher than most of ours. 111 00:08:09,447 --> 00:08:13,326 I didn't know that survival was a thing until I was 19 years old. 112 00:08:13,910 --> 00:08:18,289 I had a very atypical upbringing and grew up in a very remote environment, 113 00:08:18,372 --> 00:08:21,292 and many of the things that people consider to be survival skills 114 00:08:21,375 --> 00:08:23,794 were part of my everyday life. 115 00:08:24,670 --> 00:08:27,673 It's important for people to trust what's going on in their bodies 116 00:08:27,757 --> 00:08:31,636 as well as what their body can physically do with the outside world. 117 00:08:32,720 --> 00:08:35,890 This is why survival is important to me and important for me to teach. 118 00:08:36,933 --> 00:08:40,895 Panic, exposure and dehydration are the number one killers out here. 119 00:08:44,690 --> 00:08:47,068 So, I need to know what resources are available. 120 00:08:47,735 --> 00:08:49,487 How much water is in the area. 121 00:08:50,029 --> 00:08:53,741 If your skin isn't hydrated, it can't do what it needs to do. 122 00:08:57,078 --> 00:08:59,830 I've been in situations where I've been so dehydrated, 123 00:08:59,914 --> 00:09:03,960 I'm begging my body to continue for the potential of finding water. 124 00:09:05,002 --> 00:09:08,923 I may be climbing up some huge feature to look out for water, 125 00:09:09,006 --> 00:09:11,384 just praying that I can keep going. 126 00:09:13,135 --> 00:09:15,721 Dehydration at a level where your body doesn't wanna work, 127 00:09:15,805 --> 00:09:18,182 and you're talking yourself into every footstep. 128 00:09:20,268 --> 00:09:23,896 [narrator] As strong as it can be, the immune system's ability to protect us 129 00:09:23,980 --> 00:09:25,439 isn't unshakable. 130 00:09:25,523 --> 00:09:28,526 It depends on how healthy the body is as a whole. 131 00:09:29,277 --> 00:09:31,988 Water is essential to immune function. 132 00:09:34,323 --> 00:09:36,534 And it's monitored by the brain. 133 00:09:37,201 --> 00:09:39,036 Thirst is primarily regulated 134 00:09:39,120 --> 00:09:41,205 by a part of the brain called a hypothalamus. 135 00:09:43,082 --> 00:09:47,628 And the hypothalamus has receptors that can sense a concentration of the blood 136 00:09:47,712 --> 00:09:51,465 and decide whether we need a little more fluid to thin the blood out a little bit, 137 00:09:52,300 --> 00:09:55,428 or whether we're over-hydrated, and we don't need to drink anymore. 138 00:09:55,511 --> 00:09:57,346 The kidneys also play a role. 139 00:09:57,430 --> 00:10:00,766 So, like lots of things in the body, this is a team approach 140 00:10:00,850 --> 00:10:02,852 with multiple different organs involved. 141 00:10:06,022 --> 00:10:08,524 [narrator] The body is always paying attention to water 142 00:10:08,608 --> 00:10:11,652 because it's essential to everything. 143 00:10:11,736 --> 00:10:13,946 Especially clearing out toxins. 144 00:10:14,530 --> 00:10:16,490 Fluid is constantly flowing through us. 145 00:10:16,574 --> 00:10:21,537 Carrying bacteria and other toxins to our lymph nodes to be destroyed. 146 00:10:22,288 --> 00:10:26,167 These grape-like bunches of immune cellsare little filters 147 00:10:26,250 --> 00:10:28,252 that cleanse our internal environment. 148 00:10:29,837 --> 00:10:32,298 Dehydration backs up the system. 149 00:10:32,882 --> 00:10:36,093 Without enough water, waste can't be flushed out as efficiently, 150 00:10:36,177 --> 00:10:38,179 and immune function suffers… 151 00:10:41,557 --> 00:10:43,726 which can lead to an infection. 152 00:10:44,560 --> 00:10:47,521 [Cat] Out here, you can consume quite a bit of water, 153 00:10:47,605 --> 00:10:50,483 and still your mouth will be dry because it's so arid. 154 00:10:50,566 --> 00:10:53,152 It's important to constantly be monitoring that. 155 00:10:55,988 --> 00:10:59,158 Running water, this is golden. 156 00:11:02,828 --> 00:11:05,623 I have to boil it to kill any parasites. 157 00:11:05,706 --> 00:11:08,876 So, I won't drink it now, but I'll get some to bring with me. 158 00:11:12,129 --> 00:11:17,218 [narrator] Cat's ability to survive comes from knowing how to use natural resources 159 00:11:17,301 --> 00:11:21,430 to her advantage and understanding the limits her body can be pushed to. 160 00:11:25,393 --> 00:11:29,480 Over time, some of those limits have gotten more extreme. 161 00:11:31,232 --> 00:11:35,820 [Cat] Your body will adapt to surviving in these elements over time. 162 00:11:35,903 --> 00:11:41,033 But initially, while your body is adjusting, it's incredibly difficult. 163 00:11:41,617 --> 00:11:45,413 I've been in situations where I'm in a bad place, 164 00:11:45,496 --> 00:11:48,165 but the most important thing is that I trust my body. 165 00:11:48,874 --> 00:11:51,794 The desert's an interesting place in terms of temperature. 166 00:11:51,877 --> 00:11:54,672 It can get really, really hot during the day. 167 00:11:56,048 --> 00:11:59,051 But at night, the desert can become very, very cold 168 00:11:59,135 --> 00:12:01,512 because there's nothing to keep that heat in. 169 00:12:03,472 --> 00:12:05,933 I've literally had my water freeze during the night, 170 00:12:06,016 --> 00:12:09,353 then been in temperatures over a hundred degrees during the day. 171 00:12:12,732 --> 00:12:16,068 [narrator] After years of training, Cat's body is uniquely equipped 172 00:12:16,152 --> 00:12:21,282 to handle these massive fluctuations through a process called climatization. 173 00:12:25,870 --> 00:12:29,415 And, like hydration, it involves the brain. 174 00:12:30,499 --> 00:12:36,839 There is a capacity for the brain to regulate hormones that impact 175 00:12:36,922 --> 00:12:39,842 our body temperature, our basic homeostasis. 176 00:12:41,510 --> 00:12:43,929 [narrator] So, in the sweltering heat of the day, 177 00:12:44,013 --> 00:12:47,349 Cat's baseline body temperature is naturally higher. 178 00:12:48,058 --> 00:12:52,021 She'll also sweat more, and her sweat will be diluted more, 179 00:12:52,104 --> 00:12:54,940 which leaves more salt inside her body for energy. 180 00:12:58,152 --> 00:13:01,489 And during the freezing nights, she'll shiver less, 181 00:13:01,572 --> 00:13:04,408 allowing her to retain more heat. 182 00:13:04,492 --> 00:13:08,746 [Cat] Maintaining a core body temperature is paramount in a survival situation. 183 00:13:08,829 --> 00:13:10,498 That's why shelter's essential. 184 00:13:12,583 --> 00:13:14,710 The environment wants to suck heat from me, 185 00:13:14,794 --> 00:13:17,671 while my body's desperate to gain any heat that it can. 186 00:13:17,755 --> 00:13:20,090 So, what I'm doing is changing the environment 187 00:13:20,174 --> 00:13:23,260 so I buffered myself from the landscape. 188 00:13:26,388 --> 00:13:29,892 [narrator] It's a constant negotiation between body and nature. 189 00:13:32,436 --> 00:13:36,649 And survival means trusting that you can handle more than you think. 190 00:13:37,358 --> 00:13:40,778 [Cat] I've faced many nights wondering if I would be alive in the morning, 191 00:13:40,861 --> 00:13:43,322 with heat, with hypothermia, 192 00:13:43,405 --> 00:13:47,409 through monsoons, flash floods, through extreme dehydration. 193 00:13:51,956 --> 00:13:54,959 I think that people are innate survivors. 194 00:13:56,001 --> 00:13:58,504 I wouldn't be here right now if someone in my past 195 00:13:58,587 --> 00:14:01,799 hadn't been an excellent survivor. That's true of everyone on the planet. 196 00:14:03,175 --> 00:14:05,928 The hallmark of our species is being innovative and creative 197 00:14:06,011 --> 00:14:07,429 and overcoming and adapting. 198 00:14:08,264 --> 00:14:09,974 But we've lost faith in that ability. 199 00:14:10,057 --> 00:14:14,436 We've lost faith in our ability not to conquer nature but to live in it. 200 00:14:15,646 --> 00:14:18,566 It's really important for us to reconnect with nature 201 00:14:19,149 --> 00:14:21,443 because it teaches us something about ourselves. 202 00:14:29,994 --> 00:14:32,538 The human body is often characterized 203 00:14:32,621 --> 00:14:34,456 as being sort of weak, right? 204 00:14:36,333 --> 00:14:39,962 Like, compare ourselves to predators like lions and tigers or something. 205 00:14:40,045 --> 00:14:42,923 We don't have big sharp teeth or claws. 206 00:14:43,007 --> 00:14:45,593 We're not incredibly strong for our body size. 207 00:14:46,260 --> 00:14:49,013 So, when we think about humans that way, I'm always surprised 208 00:14:49,096 --> 00:14:53,058 by the sorts of situations that humans can survive. 209 00:14:54,560 --> 00:14:57,855 [narrator] Although raw nature feels more dangerous… 210 00:14:59,857 --> 00:15:02,234 the reality is that every environment on Earth 211 00:15:02,318 --> 00:15:05,112 is teeming with threats that we can't see. 212 00:15:07,740 --> 00:15:11,410 [Alok] Our immune system is incredibly effective at defending our bodies. 213 00:15:11,493 --> 00:15:16,206 We encounter thousands of pathogens or microbes every single day 214 00:15:16,290 --> 00:15:19,668 from kitchen counters, to doorknobs, to sitting on a subway. 215 00:15:20,502 --> 00:15:22,963 The vast majority of the time, we don't even notice. 216 00:15:26,550 --> 00:15:29,929 [narrator] But how does our body know what to do in the first place? 217 00:15:31,347 --> 00:15:35,434 And why is it that some things make us sick and others don't? 218 00:15:37,603 --> 00:15:41,565 What we do know is that everybody's immune system is different. 219 00:15:42,942 --> 00:15:45,903 And how it functions is altered constantly, 220 00:15:46,570 --> 00:15:48,697 starting from the very moment we're born. 221 00:15:52,451 --> 00:15:53,327 [whimpering] 222 00:15:55,829 --> 00:15:57,498 [country music playing] 223 00:15:58,415 --> 00:15:59,500 [neighing] 224 00:16:01,877 --> 00:16:03,671 -[Magaly] Say it together. -You start it. 225 00:16:03,754 --> 00:16:06,006 -We'll both say we're twins. -Okay, so you start. 226 00:16:06,090 --> 00:16:08,008 -Hi, I'm Magaly. -I'm Carolina. 227 00:16:08,092 --> 00:16:09,385 -We're twins. -Sorry. [chuckles] 228 00:16:09,468 --> 00:16:11,762 No, say, "And we're twins," and then look at each-- 229 00:16:14,682 --> 00:16:17,601 [Carolina] I see us as two completely different people. 230 00:16:19,228 --> 00:16:20,354 We don't dress alike. 231 00:16:20,437 --> 00:16:25,150 We don't have the same taste in, like, outfits or food or anything like that. 232 00:16:26,652 --> 00:16:28,362 [Carolina] I dress very ranch-y. 233 00:16:30,197 --> 00:16:31,532 And she's more stylish. 234 00:16:32,157 --> 00:16:33,534 She's more girly than I am. 235 00:16:33,617 --> 00:16:36,161 She loves to do her makeup and things like that. 236 00:16:37,579 --> 00:16:42,418 [Magaly] I like to go shopping. I like to go to the mall, go watch movies. 237 00:16:43,002 --> 00:16:44,169 My room's always clean. 238 00:16:45,796 --> 00:16:48,924 -Carolina's room is a mess all the time. -[laughs] 239 00:16:50,384 --> 00:16:52,845 [Carolina] If I could not go home, I would not go home. 240 00:16:52,928 --> 00:16:56,306 I would just love to be at the ranch every day, almost all the time. 241 00:16:57,474 --> 00:17:00,352 Twenty-four seven I'll be here with the horses. 242 00:17:01,854 --> 00:17:05,232 When she comes back from the ranch, she stinks. 243 00:17:05,315 --> 00:17:07,901 -[chuckles] -Um, everybody tells her to go shower. 244 00:17:10,988 --> 00:17:14,033 [narrator] Every person's immune system is like a fingerprint. 245 00:17:16,869 --> 00:17:19,580 Even if you share DNA, a house, 246 00:17:20,539 --> 00:17:23,459 or in the case of twins, a womb. 247 00:17:24,001 --> 00:17:26,045 [Robynne] People ask a lot, "What do you think it is, 248 00:17:26,128 --> 00:17:30,382 nature or nurture that can affect our susceptibility to disease?" 249 00:17:30,466 --> 00:17:32,468 The answer is, for a lot of things it's both. 250 00:17:33,218 --> 00:17:35,971 We can see within twins with the same genetic material, 251 00:17:36,597 --> 00:17:40,434 there are definitely things that are genetically predetermined, 252 00:17:41,810 --> 00:17:43,353 but they're not fixed. 253 00:17:47,649 --> 00:17:51,111 Think about why people get sick. 254 00:17:53,864 --> 00:17:56,200 If you think of the flu, tons of people are exposed. 255 00:17:56,283 --> 00:17:58,660 Some people get really sick, some get a little sick, 256 00:17:58,744 --> 00:18:00,496 and some people don't get sick at all. 257 00:18:00,579 --> 00:18:03,290 And that has a lot to do with the health of the host, 258 00:18:03,373 --> 00:18:05,250 what I like to call terrain theory. 259 00:18:06,668 --> 00:18:09,088 And your terrain is really your immune system. 260 00:18:14,927 --> 00:18:17,137 [narrator] Locked into your DNA are bits of code 261 00:18:17,221 --> 00:18:20,557 that determine things about your health long before you're born. 262 00:18:21,391 --> 00:18:26,522 Like how cancer runs in the family, or how a genetic mutation 263 00:18:26,605 --> 00:18:29,441 can help predict the likelihood you'll develop a disease. 264 00:18:30,317 --> 00:18:33,654 That's the only piece of our terrain that can't be changed. 265 00:18:34,279 --> 00:18:38,826 Then there are parts of our immune system we get just before we're born, 266 00:18:38,909 --> 00:18:40,369 from our mothers. 267 00:18:46,125 --> 00:18:47,376 [whirring] 268 00:18:49,586 --> 00:18:53,590 [Carolina] Both of my parents originated from Zacatecas, Mexico. 269 00:18:53,674 --> 00:18:55,008 [mother speaking Spanish] 270 00:18:56,051 --> 00:18:59,471 [Carolina in English] My mom was raised on a ranch and away from the city. 271 00:18:59,555 --> 00:19:01,223 So, if she was sick, 272 00:19:01,306 --> 00:19:03,308 it was an hour or two away from the doctors, 273 00:19:03,392 --> 00:19:05,602 so they had to figure everything out at home. 274 00:19:11,150 --> 00:19:12,025 It's good. 275 00:19:14,611 --> 00:19:17,156 Even now, it's very rare to see her sick. 276 00:19:18,198 --> 00:19:20,784 So, I think that me and my mom are a lot the same. 277 00:19:23,078 --> 00:19:27,124 [Alok] When mothers pass down antibodies to their fetuses, 278 00:19:27,207 --> 00:19:28,876 this is called passive immunity. 279 00:19:30,127 --> 00:19:34,464 And this is really important to protect their fetuses and their newborn babies 280 00:19:34,548 --> 00:19:36,967 when their immune systems are still developing. 281 00:19:40,345 --> 00:19:44,099 [narrator] Along with the nutrients that a baby gets from its mother in the womb, 282 00:19:44,183 --> 00:19:46,560 it also absorbs her antibodies. 283 00:19:46,643 --> 00:19:49,813 These chemicals are leftovers from infections that she's fought 284 00:19:49,897 --> 00:19:51,231 throughout her life. 285 00:19:51,315 --> 00:19:55,861 And miraculously, she's able to pass this protection on to her child 286 00:19:55,944 --> 00:19:57,029 through the placenta. 287 00:19:59,573 --> 00:20:02,075 Even if the infection happened decades ago. 288 00:20:03,869 --> 00:20:05,954 A baby won't be immune to everything, 289 00:20:06,038 --> 00:20:09,499 but enough to keep it safe for the first period of its life. 290 00:20:10,042 --> 00:20:13,212 After a few months, those antibodies start to fade 291 00:20:13,295 --> 00:20:15,881 as the baby encounters different microbes… 292 00:20:17,549 --> 00:20:19,843 and learns to fend for itself. 293 00:20:22,554 --> 00:20:24,473 What we encounter and when 294 00:20:24,556 --> 00:20:28,143 is a huge part of why everyone's immune system is different. 295 00:20:30,395 --> 00:20:32,189 [Robynne] The longer I practice medicine, 296 00:20:32,272 --> 00:20:36,318 the more I believe that nature is less significant than nurture 297 00:20:36,401 --> 00:20:37,611 for most diseases. 298 00:20:38,403 --> 00:20:41,990 And the really great thing here is that a lot of these factors 299 00:20:42,074 --> 00:20:43,242 are under our control. 300 00:20:45,452 --> 00:20:47,287 [Carolina] I was raised on a ranch. 301 00:20:48,580 --> 00:20:54,253 We would always be around cows, pigs, chickens, sheep, you name it. 302 00:20:58,048 --> 00:21:01,677 [Alok] During childhood, our bodies come in contact with all the microbes 303 00:21:01,760 --> 00:21:03,178 in our surrounding world. 304 00:21:03,262 --> 00:21:05,847 And our immune system will see this and say, 305 00:21:05,931 --> 00:21:07,516 "I'll remember that foreigner." 306 00:21:09,351 --> 00:21:11,645 [narrator] It's the same as building a muscle. 307 00:21:11,728 --> 00:21:14,481 If you don't flex it, it won't get stronger. 308 00:21:15,899 --> 00:21:18,443 When a young body has to defend against something, 309 00:21:18,527 --> 00:21:21,238 cells release antibodies that kill the threat. 310 00:21:21,989 --> 00:21:25,158 Other cells then remember how to make that antibody. 311 00:21:25,242 --> 00:21:29,246 So that if the same bug comes back, it can be killed instantly. 312 00:21:30,706 --> 00:21:34,209 These are the same antibodies that might one day be passed down 313 00:21:34,293 --> 00:21:35,836 to the next generation. 314 00:21:35,919 --> 00:21:38,505 So, the training early on as the immune system says, 315 00:21:38,588 --> 00:21:40,465 "This is nothing. We can ignore this." 316 00:21:40,549 --> 00:21:44,136 "This is super serious, red alert. We need to do something about this." 317 00:21:44,678 --> 00:21:47,431 And this training seems to be really essential. 318 00:21:49,057 --> 00:21:50,309 [guitar playing] 319 00:21:57,691 --> 00:22:01,028 [narrator] Kids who spend time in nature seem to have an advantage. 320 00:22:08,201 --> 00:22:10,287 [Carolina] I'm part of a Escaramuza team. 321 00:22:11,371 --> 00:22:15,417 Escaramuza, I could describe that as, like, the Mexican rodeo. 322 00:22:17,669 --> 00:22:21,423 It's kind of like a dance with eight girls riding on top of a horse. 323 00:22:22,924 --> 00:22:26,636 You're turning, you're spinning within each other and things like that. 324 00:22:30,474 --> 00:22:33,518 A horse isn't born to do all this. 325 00:22:33,602 --> 00:22:37,230 So, everybody has to be super focused and have good control of the horse. 326 00:22:40,984 --> 00:22:43,612 [girl] That will survive. Where did you guys go? 327 00:22:43,695 --> 00:22:46,281 [Carolina] It's very rare for me to get sick. 328 00:22:46,365 --> 00:22:50,077 And if I do get sick like, with a cold, it'll last one or two days. 329 00:22:53,121 --> 00:22:56,625 As to my sister, she'll be in bed for, like, two weeks. 330 00:22:56,708 --> 00:22:59,503 You know, she's… It hits her hard. 331 00:23:03,215 --> 00:23:05,467 [Magaly] When I was in high school, I did get sick. 332 00:23:05,967 --> 00:23:10,222 I stayed home for, like, a month. I think I had, like, a respiratory virus. 333 00:23:10,806 --> 00:23:12,307 It was not fun. 334 00:23:13,392 --> 00:23:16,812 [Robynne] Kids who are not exposed to enough germs early on 335 00:23:16,895 --> 00:23:18,647 are really at a disadvantage, 336 00:23:18,730 --> 00:23:21,316 and are at a higher risk for developing disease 337 00:23:21,400 --> 00:23:23,902 because their immune system doesn't know what to do 338 00:23:23,985 --> 00:23:25,445 when it sees something later on. 339 00:23:28,698 --> 00:23:32,244 [narrator] As we age, the training that happens in our immune system 340 00:23:32,327 --> 00:23:36,164 involves a wide range of different cells with different jobs. 341 00:23:36,915 --> 00:23:40,919 But there's one type of cell that carries most of the weight. 342 00:23:43,797 --> 00:23:47,175 [Alok] T-cells are the powerhouse cells of our immune system. 343 00:23:49,386 --> 00:23:52,347 They help make antibodies against other diseases. 344 00:23:52,431 --> 00:23:55,559 They work with signaling to other parts of the immune system. 345 00:23:55,642 --> 00:23:58,812 They can kill cells that are bad on their own. 346 00:24:00,063 --> 00:24:03,775 They also can remember things. So, they have a memory component to them too 347 00:24:03,859 --> 00:24:07,070 to prevent future infections or diseases. 348 00:24:09,990 --> 00:24:13,452 [narrator] Like all blood, these cells are born in the bone marrow. 349 00:24:14,202 --> 00:24:16,621 Then they migrate to the thymus gland. 350 00:24:17,456 --> 00:24:21,501 It's here that T-cells go through serious training, 351 00:24:21,585 --> 00:24:23,336 and they pick up different skills. 352 00:24:24,379 --> 00:24:27,507 Some T-cells leave the thymus as assassins. 353 00:24:28,842 --> 00:24:30,927 Others come out as intelligence, 354 00:24:31,011 --> 00:24:35,849 capable of remembering a virus for fast detection and fast execution. 355 00:24:38,185 --> 00:24:41,646 Because of all this action, the thymus is larger in kids. 356 00:24:42,397 --> 00:24:44,274 And it peaks in our teenage years. 357 00:24:49,070 --> 00:24:52,782 [Carolina] What I love about being here the most is the bonding with the horses… 358 00:24:56,661 --> 00:24:57,496 grooming him… 359 00:24:58,705 --> 00:24:59,873 washing him… 360 00:25:01,708 --> 00:25:03,084 sweeping, mopping. 361 00:25:04,669 --> 00:25:07,172 By the end of the day, I'm extremely dirty. 362 00:25:07,255 --> 00:25:09,466 My sweat, the horse's sweat. 363 00:25:10,050 --> 00:25:12,135 It's a very messy job, but I love it. 364 00:25:15,889 --> 00:25:19,851 I see so many parallels between the animal kingdom and us, 365 00:25:19,935 --> 00:25:22,979 and I see that as we differentiate our self more and more, 366 00:25:23,063 --> 00:25:24,940 we're actually getting sicker and sicker. 367 00:25:25,565 --> 00:25:32,072 So, I try to look at what's going on in the natural world, and what animals do. 368 00:25:34,199 --> 00:25:38,995 Horses take dirt baths because there are ammonia-oxidizing bacteria in the dirt 369 00:25:39,079 --> 00:25:41,998 that can neutralize the sweat and help clean them. 370 00:25:43,124 --> 00:25:45,001 Getting out and getting sweaty, 371 00:25:45,085 --> 00:25:47,546 all the things that work so well in the animal kingdom, 372 00:25:47,629 --> 00:25:49,881 I think work really well for us as humans. 373 00:25:57,514 --> 00:26:01,101 [narrator] Exposure to animals can give the young immune system a boost… 374 00:26:04,604 --> 00:26:06,147 but it's a double-edged sword. 375 00:26:06,815 --> 00:26:11,194 Animals are also the source of some of our most devastating diseases. 376 00:26:12,404 --> 00:26:15,740 [Alok] Zoonotic diseases come in many shapes and sizes, 377 00:26:15,824 --> 00:26:17,826 and some are really, really creepy. 378 00:26:18,785 --> 00:26:20,954 What happens is you have an animal host, 379 00:26:21,037 --> 00:26:24,165 and then something that transmits it to a human. 380 00:26:24,249 --> 00:26:25,834 It could be a spider or a mosquito. 381 00:26:26,751 --> 00:26:29,254 This represents a huge public health threat 382 00:26:29,337 --> 00:26:31,089 that could get worse in the future. 383 00:26:32,215 --> 00:26:33,883 [narrator] The bubonic plague. 384 00:26:33,967 --> 00:26:34,884 Malaria. 385 00:26:35,635 --> 00:26:36,469 Swine flu. 386 00:26:37,262 --> 00:26:38,096 Zika. 387 00:26:38,722 --> 00:26:39,556 COVID-19. 388 00:26:40,140 --> 00:26:44,311 Many of our most lethal outbreaks can be traced to wildlife… 389 00:26:46,187 --> 00:26:50,442 and how close we live to animals and to each other plays a huge role. 390 00:26:51,401 --> 00:26:54,237 That's something that wasn't true for our ancestors. 391 00:26:54,821 --> 00:26:57,157 [Melanie] If you look at foraging people or hunter-gatherers, 392 00:26:57,240 --> 00:27:00,201 the significance of infectious disease is relatively low. 393 00:27:00,744 --> 00:27:05,790 Today, you have a lot of individuals that live in very large groups 394 00:27:05,874 --> 00:27:08,209 in close proximity and interacting with each other, 395 00:27:08,293 --> 00:27:12,047 then that does breed conditions for pandemic disease. 396 00:27:13,673 --> 00:27:17,927 [narrator] As our population grows, outbreaks are becoming more frequent. 397 00:27:20,555 --> 00:27:22,807 If hindsight is 20/20, 398 00:27:22,891 --> 00:27:28,396 what can we learn from those who faced past plagues and lived to tell the tale? 399 00:27:31,775 --> 00:27:33,109 [heart beating] 400 00:27:36,237 --> 00:27:39,157 [Adaora Okoli] I had a sense of being out of my body. 401 00:27:42,619 --> 00:27:49,125 I was feverish, had joint aches and pains, copious vomiting, and diarrhea. 402 00:27:50,835 --> 00:27:52,337 I didn't realize how sick I felt 403 00:27:52,420 --> 00:27:55,256 until my mother came to the isolation center to see me. 404 00:27:56,841 --> 00:27:59,552 And she said I looked like I was a zombie. 405 00:28:03,223 --> 00:28:04,516 My name is Adaora Okoli. 406 00:28:04,599 --> 00:28:07,936 I'm a medical doctor interested in infectious diseases. 407 00:28:08,478 --> 00:28:11,272 And I survived Ebola in 2014. 408 00:28:16,194 --> 00:28:19,322 [narrator] Viruses cause millions of deaths every year. 409 00:28:20,699 --> 00:28:24,202 But most of them come from diseases that we are familiar with, 410 00:28:24,285 --> 00:28:26,371 like the flu or HIV. 411 00:28:27,247 --> 00:28:31,376 So, when a disease that's been lurking quietly in an obscure cave 412 00:28:31,459 --> 00:28:34,045 suddenly jumps to a human and starts to spread, 413 00:28:34,921 --> 00:28:36,131 it's cause for alarm. 414 00:28:39,217 --> 00:28:42,137 Especially if it happens in a place with limited resources. 415 00:28:46,433 --> 00:28:47,767 [Adaora] Growing up in Nigeria, 416 00:28:49,018 --> 00:28:52,355 I fell in love with medicine and the idea of helping people. 417 00:28:54,899 --> 00:28:57,819 A lot of people really didn't have access to health care. 418 00:28:59,404 --> 00:29:03,199 If you were in an emergency situation, and you didn't have the money to pay, 419 00:29:03,283 --> 00:29:04,743 you couldn't see the doctor. 420 00:29:05,702 --> 00:29:09,956 And I, you know, felt that, you know, being a doctor would be on the side 421 00:29:10,039 --> 00:29:11,958 where I could be able to help people. 422 00:29:15,086 --> 00:29:19,382 When I finished medical school, I started working as a medical officer, 423 00:29:19,466 --> 00:29:23,219 and it was during that time that the Ebola outbreak struck in West Africa. 424 00:29:27,474 --> 00:29:32,353 [reporter] Ebola virus has already killed over 3,000 people across West Africa. 425 00:29:32,437 --> 00:29:35,607 [reporter 2] A growing number of health workers are falling victim to the disease, 426 00:29:35,690 --> 00:29:39,861 adding yet more pressure to an epidemic the WHO has called the most severe 427 00:29:39,944 --> 00:29:43,156 acute public health emergency in modern times. 428 00:29:44,783 --> 00:29:48,745 [narrator] Although deadly outbreaks end up being remembered as epic battles, 429 00:29:48,828 --> 00:29:52,499 every major epidemic that has brought humanity to its knees 430 00:29:52,582 --> 00:29:56,252 can be traced back to something imperceptibly small. 431 00:29:58,505 --> 00:30:01,758 There are some pathogens which are really aggressive or dangerous, 432 00:30:01,841 --> 00:30:04,677 and a lot of it has to do with their mechanism of action, 433 00:30:04,761 --> 00:30:06,179 or how they attack our bodies. 434 00:30:09,766 --> 00:30:12,769 [Nina] A cell is, you know, most simply speaking, 435 00:30:12,852 --> 00:30:15,814 the basic unit of life. 436 00:30:15,897 --> 00:30:18,733 It's the smallest functional unit that life can be. 437 00:30:18,817 --> 00:30:21,986 You could argue that viruses are a little smaller. 438 00:30:23,488 --> 00:30:28,284 [Alok] A virus is this little biological agent that has one central goal: 439 00:30:29,285 --> 00:30:34,374 to get inside of cells, reproduce itself, and then spread to another host. 440 00:30:34,457 --> 00:30:36,793 And along the way, it can cause a lot of damage. 441 00:30:38,127 --> 00:30:42,340 [narrator] Viruses emerged from the ether about 1.5 billion years ago. 442 00:30:45,677 --> 00:30:48,346 And the fact that they've been around so long means 443 00:30:49,097 --> 00:30:50,932 they're really good at what they do. 444 00:30:52,225 --> 00:30:54,227 When a virus enters a host cell… 445 00:30:58,439 --> 00:31:03,903 it hijacks it, causing it to spit out copy after copy of new virus particles 446 00:31:04,529 --> 00:31:07,407 that burst out of the cell into the bloodstream. 447 00:31:13,705 --> 00:31:17,542 A virus doesn't just want to colonize that single host. 448 00:31:17,625 --> 00:31:19,961 It wants to spread through populations. 449 00:31:21,504 --> 00:31:26,342 [Alok] What made the 2014 outbreak of Ebola widespread and so dangerous 450 00:31:26,426 --> 00:31:29,345 is people were contracting the disease without even knowing it. 451 00:31:29,429 --> 00:31:31,639 By that time, there were land crossings happening 452 00:31:31,723 --> 00:31:33,808 between Guinea, Liberia and Sierra Leone. 453 00:31:34,392 --> 00:31:38,688 And the disease built a community base and was spreading before alarms went off. 454 00:31:40,857 --> 00:31:43,818 [narrator] And that type of growth gets out of hand quickly. 455 00:31:46,487 --> 00:31:48,781 Say you start with one sick person. 456 00:31:49,407 --> 00:31:51,784 If that number doubles every three days, 457 00:31:52,452 --> 00:31:57,332 you're going to end up with 67 million infections in under three months. 458 00:31:59,459 --> 00:32:01,461 [Adaora] On the 20th of July 2014, 459 00:32:02,587 --> 00:32:05,298 I was working in a private hospital in Nigeria 460 00:32:05,381 --> 00:32:10,303 when a Liberian diplomat was brought into the hospital with mysterious symptoms. 461 00:32:11,930 --> 00:32:13,598 And when I saw him in bed, 462 00:32:13,681 --> 00:32:16,893 he had his IV bag right next to him. 463 00:32:16,976 --> 00:32:20,104 The first thing I did was pick up the IV bag and put it on the stand. 464 00:32:22,523 --> 00:32:27,236 And that might have been the route of entry into my system. 465 00:32:30,031 --> 00:32:31,950 Twenty-four hours later, I got a call. 466 00:32:32,659 --> 00:32:34,619 The patient had tested positive. 467 00:32:34,702 --> 00:32:38,831 He had Ebola, and 24 hours after we had the result, 468 00:32:38,915 --> 00:32:41,501 the patient was found dead in his bedroom. 469 00:32:43,419 --> 00:32:46,798 At that point, the fear was more than we could handle. 470 00:32:48,424 --> 00:32:50,218 It could be any of us the next day. 471 00:32:52,929 --> 00:32:56,140 [narrator] Ebola is an incredibly infectious disease. 472 00:32:57,141 --> 00:32:59,811 That means that in every drop of infected fluid 473 00:32:59,894 --> 00:33:02,480 there are millions of viral particles. 474 00:33:02,563 --> 00:33:05,900 So, if you come into contact with someone who has it, 475 00:33:05,984 --> 00:33:09,153 it takes almost nothing to start an infection. 476 00:33:11,531 --> 00:33:13,032 [Adaora] Shortly after that, 477 00:33:13,741 --> 00:33:19,163 I started to have joint aches and pain, sore throat, loss of appetite. 478 00:33:19,247 --> 00:33:20,581 Yeah, I was feverish. 479 00:33:21,332 --> 00:33:23,251 I had vomiting and diarrhea. 480 00:33:23,793 --> 00:33:25,003 And I thought 481 00:33:26,212 --> 00:33:27,171 this is it. 482 00:33:27,255 --> 00:33:28,423 This is really it. 483 00:33:30,883 --> 00:33:34,721 [Alok] A virus like Ebola is extremely lethal 484 00:33:34,804 --> 00:33:38,599 because Ebola is specifically designed to evade our immune system 485 00:33:38,683 --> 00:33:41,060 and even mess with cell signaling in our bodies. 486 00:33:41,936 --> 00:33:45,982 It basically can hijack a ride throughout our lymphatic and bloodstream, 487 00:33:46,065 --> 00:33:50,069 infect our bodies, and it's way too late when our immune systems finally pick up 488 00:33:50,153 --> 00:33:51,195 on what's happening. 489 00:33:53,906 --> 00:33:57,118 [narrator] Ebola's assault is merciless. 490 00:33:57,201 --> 00:34:01,664 It attacks the gastrointestinal tract, causing diarrhea and dehydration. 491 00:34:02,540 --> 00:34:04,250 It attacks the kidneys, 492 00:34:04,333 --> 00:34:07,295 which make it more difficult for the body to produce plasma. 493 00:34:07,879 --> 00:34:10,757 And finally, the virus releases proteins 494 00:34:10,840 --> 00:34:14,927 that damage the lining of blood vessels, which then start to leak. 495 00:34:16,846 --> 00:34:19,724 That's why the disease has a reputation of causing victims 496 00:34:19,807 --> 00:34:21,517 to bleed from every orifice. 497 00:34:23,561 --> 00:34:26,773 The blood vessel damage leads to a drop in blood pressure… 498 00:34:27,940 --> 00:34:29,859 multiple organ failure follows… 499 00:34:31,819 --> 00:34:32,653 then death. 500 00:34:39,035 --> 00:34:41,454 [Adaora] I was led to the isolation center. 501 00:34:42,538 --> 00:34:43,664 It was a dark room. 502 00:34:45,041 --> 00:34:47,668 In an abandoned building that hadn't been used for years. 503 00:34:51,130 --> 00:34:54,217 Every Ebola patient has a moment of denial 504 00:34:54,300 --> 00:34:57,678 because nine out of ten people who have Ebola die. 505 00:34:58,304 --> 00:35:04,060 What are the odds that I would be the one out of ten who would survive? 506 00:35:05,478 --> 00:35:09,357 But I was using my clinical knowledge at that time as a doctor. 507 00:35:09,440 --> 00:35:12,193 What kills people is when they lose so much fluid, 508 00:35:12,276 --> 00:35:16,656 and their system becomes overwhelmed with the virus, which has replicated. 509 00:35:17,156 --> 00:35:18,282 That's when they die. 510 00:35:18,366 --> 00:35:20,034 So, I thought to myself, 511 00:35:20,118 --> 00:35:22,995 "I have to really drink this oral rehydration solution." 512 00:35:23,913 --> 00:35:27,625 I had a bottle in my hand every time, even when I was asleep. 513 00:35:27,708 --> 00:35:30,253 I had a bottle right next to me just in case I vomited, 514 00:35:30,336 --> 00:35:31,879 I could replace my fluids. 515 00:35:32,880 --> 00:35:36,884 I could only hope that my immune system was strong enough to fight the virus. 516 00:35:38,719 --> 00:35:42,348 [narrator] Even on its last legs, our immune system keeps fighting. 517 00:35:44,058 --> 00:35:47,478 T-cells hone in on Ebola-infected cells. 518 00:35:48,271 --> 00:35:51,190 They bind to the surface and release toxins 519 00:35:51,274 --> 00:35:53,985 that travel through the cell's membrane and kill them. 520 00:35:58,072 --> 00:36:01,534 Other cells fire chemical missiles in the form of antibodies 521 00:36:01,617 --> 00:36:03,870 to stop the virus in its tracks. 522 00:36:04,912 --> 00:36:07,039 As the immune systems gain the upper hand, 523 00:36:07,665 --> 00:36:09,667 the body's systems come back online… 524 00:36:11,460 --> 00:36:14,255 and damaged tissue starts to heal. 525 00:36:15,214 --> 00:36:20,845 [Adaora] Most people who survived usually got better after seven days or so. 526 00:36:20,928 --> 00:36:22,430 So it was a matter of time. 527 00:36:27,018 --> 00:36:32,064 After five days, I noticed that my symptoms were starting to get better. 528 00:36:32,690 --> 00:36:35,776 Fourteen days later, my blood sample tested negative. 529 00:36:36,736 --> 00:36:40,615 And that was… It was the happiest day of my life. 530 00:36:42,867 --> 00:36:44,535 It was like being born again. 531 00:36:45,119 --> 00:36:46,245 It was a rebirth. 532 00:36:51,542 --> 00:36:55,046 [Alok] The Ebola outbreak in 2014 was eventually brought under control 533 00:36:55,671 --> 00:36:58,883 when we had international efforts to understand, 534 00:36:58,966 --> 00:37:01,177 quarantine people who are affected, 535 00:37:01,260 --> 00:37:04,013 and help prevent the spread of future cases. 536 00:37:04,597 --> 00:37:08,184 [narrator] And that's because what we think of as Ebola's strength 537 00:37:08,267 --> 00:37:10,102 is actually its weakness. 538 00:37:11,103 --> 00:37:13,856 It's so deadly, that victims died 539 00:37:13,940 --> 00:37:17,652 before infecting enough people for it to spread widely. 540 00:37:19,195 --> 00:37:23,950 For Dr. Okoli, her firsthand experience with the horror of Ebola 541 00:37:24,033 --> 00:37:27,411 caused her to shift focus towards fighting future epidemics. 542 00:37:28,246 --> 00:37:29,914 [Adaora] Since surviving Ebola, 543 00:37:30,039 --> 00:37:35,044 I came to New Orleans training in Internal Medicine at Tulane University. 544 00:37:37,213 --> 00:37:41,968 Hi, good afternoon. I'm Dr. Okoli. What brings you to the hospital today? 545 00:37:42,051 --> 00:37:45,388 I've been having a dry cough, and it's been coming in at night. 546 00:37:45,471 --> 00:37:48,391 [Adaora] I have shifted my focus towards infectious disease 547 00:37:48,474 --> 00:37:50,434 and global health advocacy. 548 00:37:52,019 --> 00:37:55,731 Specifically looking at how we can reduce the burden of infectious diseases 549 00:37:55,815 --> 00:37:57,316 in low-income communities. 550 00:37:57,400 --> 00:38:02,154 We're in an age now where viruses do not respect geographical locations. 551 00:38:03,114 --> 00:38:04,657 They do not respect race. 552 00:38:05,241 --> 00:38:06,742 They don't respect age. 553 00:38:09,203 --> 00:38:12,581 We're in a world and a time when people are mobile, 554 00:38:12,665 --> 00:38:14,959 and all it takes is one person to hop into a plane 555 00:38:15,042 --> 00:38:17,211 and fly thousands of miles away. 556 00:38:22,842 --> 00:38:25,219 It's no longer them and us. 557 00:38:27,596 --> 00:38:29,181 We're all in this together. 558 00:38:34,020 --> 00:38:37,565 [narrator] The destruction from an epidemic can have ripple effects 559 00:38:37,648 --> 00:38:39,942 across continents and generations. 560 00:38:40,735 --> 00:38:44,196 But given how many bugs are floating around in nature, 561 00:38:44,280 --> 00:38:46,365 these events are still pretty rare. 562 00:38:47,992 --> 00:38:52,538 In fact, there's a lot more danger potentially lurking within our own cells. 563 00:38:54,874 --> 00:38:59,128 Something that's just starting to become understood is, 564 00:38:59,211 --> 00:39:03,132 "Why does the immune system sometimes attack our own bodies 565 00:39:03,215 --> 00:39:06,594 instead of threats that come from outside?" 566 00:39:06,677 --> 00:39:12,391 "Why is it that our immune system is not good at recognizing cancer?" 567 00:39:13,225 --> 00:39:16,354 "Why do our own cells sometimes go off script?" 568 00:39:18,356 --> 00:39:21,484 [narrator] The immune system has to constantly strike a balance 569 00:39:21,567 --> 00:39:25,654 between killing intruders without damaging the body in the process. 570 00:39:26,655 --> 00:39:31,702 And when the threat comes from our own cells, that job gets even harder. 571 00:39:34,038 --> 00:39:38,084 So, now, the cutting edge of immune science is a quest to understand 572 00:39:38,167 --> 00:39:41,212 how we can harness the power of the immune system 573 00:39:41,295 --> 00:39:44,465 when it's our own bodies who are the enemy. 574 00:39:49,887 --> 00:39:53,307 [Milton Wright] The only thing I remember is going into the hospital, 575 00:39:53,391 --> 00:39:54,642 them putting me to sleep, 576 00:39:54,767 --> 00:39:59,480 and then waking up to needles and tubes and machines all around me. 577 00:40:01,857 --> 00:40:04,193 I just remember my mom crying on the side of the bed 578 00:40:04,276 --> 00:40:05,945 and saying, "You have cancer." 579 00:40:08,322 --> 00:40:11,534 And to an eight-year-old, I wasn't really sure what cancer is. 580 00:40:13,661 --> 00:40:14,912 My name is Milton Wright. 581 00:40:14,995 --> 00:40:18,958 I'm 26 years old, and I'm a three-time cancer survivor. 582 00:40:21,836 --> 00:40:23,796 I'm an active person. 583 00:40:23,879 --> 00:40:28,926 I'm usually boxing or kickboxing or going out for jogs. 584 00:40:30,553 --> 00:40:35,850 And growing up, I just ran around all day around the neighborhood playing football. 585 00:40:37,560 --> 00:40:41,772 When I was about eight, I just started having intensive pains. 586 00:40:46,193 --> 00:40:48,279 And I just wasn't able to walk anymore. 587 00:40:49,196 --> 00:40:51,198 I wasn't eating, wasn't drinking. 588 00:40:51,282 --> 00:40:54,201 My weight was down to my two-year-old little sister when I was 8. 589 00:40:54,952 --> 00:40:56,662 Obviously, something was way off. 590 00:41:01,625 --> 00:41:04,170 I was diagnosed with leukemia, 591 00:41:04,253 --> 00:41:08,674 a cancer that forms in the bone marrow and spreads out and through your blood 592 00:41:09,300 --> 00:41:11,051 destroying your cells in your body. 593 00:41:14,805 --> 00:41:17,099 [Nina] Our DNA is really just a molecule. 594 00:41:19,185 --> 00:41:22,813 It's not perfect. It's prone to getting damage over time. 595 00:41:28,152 --> 00:41:30,070 And if the DNA in our cells get damaged, 596 00:41:30,696 --> 00:41:34,575 then they could lose their ability to perfectly divide. 597 00:41:37,328 --> 00:41:39,747 [narrator] Our cells come with an internal clock… 598 00:41:42,625 --> 00:41:44,835 that tells them when to divide and grow… 599 00:41:46,378 --> 00:41:48,172 and when to slow down and die. 600 00:41:52,009 --> 00:41:57,139 But occasionally, a switch gets flipped that says, "Keep dividing. Don't stop." 601 00:41:59,266 --> 00:42:04,688 When cells don't die as planned, they crowd out and kill healthy cells… 602 00:42:06,941 --> 00:42:09,068 disrupting the body's complex balance. 603 00:42:13,364 --> 00:42:17,284 When that happens, it's the immune system that steps in. 604 00:42:19,662 --> 00:42:24,166 In fact, every day, your immune system snuffs out the spark of cancer 605 00:42:24,667 --> 00:42:26,085 without you ever knowing it. 606 00:42:27,962 --> 00:42:30,839 The irony of leukemia, the sad irony, 607 00:42:30,923 --> 00:42:34,802 is that sometimes these cancer-fighting cells go rogue. 608 00:42:38,722 --> 00:42:42,726 White blood cells in the bone marrow start to divide unceasingly, 609 00:42:42,810 --> 00:42:47,731 disrupting blood production and causing a system-wide breakdown. 610 00:42:50,568 --> 00:42:53,487 [Milton] They ended up immediately putting me into a three-and-a-half-year 611 00:42:53,571 --> 00:42:54,905 chemotherapy treatment. 612 00:42:58,242 --> 00:43:02,621 Chemotherapy is gonna break the body down no matter who you are. 613 00:43:03,247 --> 00:43:06,292 [chuckles] Doesn't matter if you're built like Mike Tyson. 614 00:43:06,375 --> 00:43:07,668 Like, it doesn't matter. 615 00:43:10,963 --> 00:43:15,801 It can get to a point where the chemo itself is worse than the cancer. 616 00:43:18,345 --> 00:43:19,597 I'm Rebecca Gardner. 617 00:43:19,680 --> 00:43:21,974 I'm an associate professor at the University of Washington 618 00:43:22,057 --> 00:43:23,309 and a pediatric oncologist. 619 00:43:24,226 --> 00:43:26,353 Historically, the way we've treated cancer 620 00:43:26,437 --> 00:43:28,272 is we have developed chemotherapies, 621 00:43:28,355 --> 00:43:30,316 which target cells that are growing quickly. 622 00:43:31,191 --> 00:43:33,611 They're effective at treating cancer but not specific, 623 00:43:33,694 --> 00:43:37,072 meaning that they will target a lot of your healthy tissues as well. 624 00:43:37,156 --> 00:43:39,116 And in kids, that's a big issue 625 00:43:39,199 --> 00:43:41,619 because a lot of their cells are growing quickly. 626 00:43:44,747 --> 00:43:47,916 And so chemotherapy can have devastating long-term consequences. 627 00:43:52,463 --> 00:43:55,007 [Milton] After finally being in the clear when I was 12, 628 00:43:55,090 --> 00:43:58,093 you get back to normal life as much as possible… 629 00:44:00,179 --> 00:44:02,973 but then I relapsed when I was 15 years old. 630 00:44:05,643 --> 00:44:08,187 And I relapsed again when I was about 20 years old. 631 00:44:13,525 --> 00:44:17,821 A third time, it's pretty much like, that's… That's it. 632 00:44:19,865 --> 00:44:21,283 You're not going to make it. 633 00:44:22,201 --> 00:44:25,537 After all that happened, the doctor came back in and she was like, 634 00:44:25,621 --> 00:44:31,168 "We have this study where we use your immune system to fight off the cancer." 635 00:44:34,296 --> 00:44:37,049 The concept of immunotherapy sounds very sci-fi. 636 00:44:37,132 --> 00:44:39,510 At the heart of it, it's a very simple idea. 637 00:44:41,178 --> 00:44:43,681 Our immune system is designed to protect us. 638 00:44:47,643 --> 00:44:50,604 The issue is that cancer usually comes from your own body. 639 00:44:50,688 --> 00:44:53,982 And so your immune system is not educated to recognize it as bad. 640 00:44:54,692 --> 00:44:57,653 So, immunotherapy is really exploiting your immune system 641 00:44:57,736 --> 00:45:00,030 to recognize your cancer cells as being bad. 642 00:45:02,408 --> 00:45:04,368 [Nina] Cancer is a cellular disease, 643 00:45:04,451 --> 00:45:08,956 and each of those cells have their own intelligence. 644 00:45:12,209 --> 00:45:15,713 Interacting with our bodies on that level as ecosystems, 645 00:45:15,796 --> 00:45:18,424 composed of trillions of cells, 646 00:45:19,216 --> 00:45:25,264 I think can open up a whole new way to view health and disease 647 00:45:25,347 --> 00:45:27,349 that is much more nuanced. 648 00:45:30,477 --> 00:45:34,064 [narrator] A century ago, scientists realized they could treat cancer 649 00:45:34,148 --> 00:45:37,484 by intentionally triggering their patient's immune system. 650 00:45:37,568 --> 00:45:40,404 Like by injecting them with a bacteria or virus. 651 00:45:46,118 --> 00:45:50,539 Now gene editing technology is allowing us to educate the immune system 652 00:45:50,622 --> 00:45:55,419 on the level of DNA to target cancer with a new and extreme precision. 653 00:45:58,213 --> 00:46:01,008 [Rebecca] We felt like Milton was a good candidate for this treatment, 654 00:46:01,091 --> 00:46:03,093 because he'd gotten chemotherapy a couple of times, 655 00:46:03,177 --> 00:46:05,262 and each time his leukemia came back. 656 00:46:07,681 --> 00:46:10,434 Anytime a treatment is new, you're guarded. 657 00:46:10,517 --> 00:46:13,145 You think, "Even though all of this stuff looks good, 658 00:46:13,228 --> 00:46:15,355 we're not sure if it's actually gonna work." 659 00:46:18,192 --> 00:46:21,236 But Milton was like, "Okay, sounds good. Where do I sign?" 660 00:46:24,156 --> 00:46:28,035 You kind of go in blind, but it's that or, you know, nothing, so… 661 00:46:28,118 --> 00:46:29,244 [scoffs] 662 00:46:34,416 --> 00:46:36,752 [Rebecca] In Seattle, he was the second patient 663 00:46:36,835 --> 00:46:38,670 that we had ever done this for. 664 00:46:41,965 --> 00:46:43,967 [narrator] Milton's immunotherapy began 665 00:46:44,051 --> 00:46:46,512 with his T-cells being extracted from his blood. 666 00:46:49,097 --> 00:46:51,266 The DNA of the cells was then edited. 667 00:46:52,184 --> 00:46:56,396 Imagine it's like changing someone's eyes from blue to brown. 668 00:46:57,314 --> 00:47:01,568 In this case, they changed the surface of the T-cells so that the cancer cells 669 00:47:01,652 --> 00:47:05,531 would recognize them, bind to them, and be killed. 670 00:47:08,700 --> 00:47:11,036 The mutated T-cells were then injected 671 00:47:11,119 --> 00:47:14,832 back into Milton's bloodstream and unleashed. 672 00:47:21,922 --> 00:47:25,467 [Milton] A couple of days after that, I started getting flu-like symptoms. 673 00:47:25,968 --> 00:47:27,427 And they were like, "Yes!" 674 00:47:30,222 --> 00:47:32,850 [narrator] To confirm the immunotherapy is working, 675 00:47:32,933 --> 00:47:36,728 doctors look for fevers, aches, and nausea. 676 00:47:38,063 --> 00:47:41,733 These symptoms are caused by chemical signals the immune system sends 677 00:47:41,817 --> 00:47:43,443 to rally the troops. 678 00:47:45,237 --> 00:47:50,325 Inside Milton's body, his reprogrammed immune cells were on the offensive. 679 00:47:51,451 --> 00:47:54,538 Attaching to and killing his leukemia. 680 00:47:56,623 --> 00:47:58,542 [Milton] I think it took three months, 681 00:47:58,625 --> 00:48:00,836 then one day they came in and they were like, 682 00:48:01,378 --> 00:48:02,671 "Good news. It's gone." 683 00:48:04,715 --> 00:48:07,009 They were like, "You're officially cancer-free." 684 00:48:11,513 --> 00:48:15,559 You look at Milton, who had really been failed by chemotherapy. 685 00:48:17,769 --> 00:48:19,479 We came up with this new therapy, 686 00:48:19,563 --> 00:48:20,939 and we were able to do it. 687 00:48:21,023 --> 00:48:23,233 We were able to get him into remission. 688 00:48:24,693 --> 00:48:25,986 -Hey, hey. -[Milton] Hi, again. 689 00:48:26,737 --> 00:48:29,072 I'm surprised you're out of work, out of the office. 690 00:48:29,156 --> 00:48:31,116 I know, it's amazing. 691 00:48:31,199 --> 00:48:33,493 [Milton] What has it been? Like, six years now, right? 692 00:48:33,577 --> 00:48:34,411 [Rebecca] Yeah. 693 00:48:35,287 --> 00:48:38,540 [Milton] I'm very thankful for her because if it wasn't for her, 694 00:48:39,958 --> 00:48:42,294 you know, I would be six feet under. 695 00:48:44,171 --> 00:48:47,132 -I was taking, like, 110 pills a day. -I know, right? 696 00:48:47,215 --> 00:48:49,217 -You don't take any medicines now. -[Milton] Nope. 697 00:48:49,301 --> 00:48:52,304 And just think, like, when you walk by somebody, they have no idea. 698 00:48:53,513 --> 00:48:56,934 Right now, about half the people who respond stay in remission. 699 00:48:57,017 --> 00:48:59,394 Our hope is to stay one step ahead of everybody. 700 00:48:59,478 --> 00:49:01,188 So, "Okay, this is your trial now, 701 00:49:01,271 --> 00:49:03,982 but if this one doesn't work for you, we have this next one." 702 00:49:06,318 --> 00:49:11,198 It feels good knowing that I can give back to what the nurses and doctors gave to me, 703 00:49:11,281 --> 00:49:12,491 which was life. 704 00:49:16,244 --> 00:49:19,539 I'm actually working at Seattle Children's Hospital now. 705 00:49:20,457 --> 00:49:24,127 So, I did a full 360 from being a patient 706 00:49:24,211 --> 00:49:29,216 to now I work with those same patients that I once was. 707 00:49:34,554 --> 00:49:35,973 [Rebecca] We've learned so much 708 00:49:36,056 --> 00:49:40,102 that we're actually able to use the immune system to treat cancer. 709 00:49:40,185 --> 00:49:42,104 I think when you look into the future, 710 00:49:42,187 --> 00:49:44,481 that's what the future of oncology is gonna be. 711 00:49:45,232 --> 00:49:47,609 It's not gonna be chemotherapy and radiation. 712 00:49:47,693 --> 00:49:51,655 It's gonna be very precision medicine. It's gonna be immunotherapy. 713 00:49:53,657 --> 00:49:59,413 [Milton] To know that you can have something that is not foreign to your body 714 00:49:59,496 --> 00:50:03,667 protect you and defeat the cancer cells inside you, 715 00:50:03,750 --> 00:50:05,585 just feels empowering. [chuckles] 716 00:50:13,719 --> 00:50:15,971 Look at what humans have gone through throughout history. 717 00:50:17,931 --> 00:50:21,852 From famine, natural disasters, disease. 718 00:50:24,479 --> 00:50:28,025 We have this incredible ability to adapt to our circumstances 719 00:50:28,108 --> 00:50:29,901 and persevere as a species. 720 00:50:31,153 --> 00:50:33,113 I think we're incredibly resilient. 721 00:50:36,241 --> 00:50:40,871 [narrator] Our ability to survive goes back to the limitless potential 722 00:50:40,954 --> 00:50:41,830 of this system. 723 00:50:44,166 --> 00:50:48,420 I've developed a really intuitive sense 724 00:50:48,503 --> 00:50:51,506 of trust that the cells know what to do. 725 00:50:54,217 --> 00:50:59,639 But we have the potential to amplify our body's natural ability to heal. 726 00:51:01,808 --> 00:51:05,312 To move past repair of the body. 727 00:51:06,605 --> 00:51:10,942 And think about the next level, which is true healing. 728 00:51:15,697 --> 00:51:17,282 [theme music playing]