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Pratique du shadowing : The Immune System Explained I - Bacteria Infection

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  1. Every second of your life you are under attack.0:00
  2. Billions of bacteria, viruses and fungi are trying to make you their home.0:03
  3. Still, our bodies have developed a super complex little army with guards, soldiers, intelligence, weapons factories and communicators to protect you from, well, dying.0:07
  4. For this video, let's assume the immune system has 12 different jobs.0:17
  5. For example, kill enemies, communicate, etc.0:21
  6. And it has 21 different cells and two protein forces.0:25
  7. These cells have up to four different jobs.0:29
  8. Let's assign them.0:32
  9. Here are the interactions.0:33
  10. Now, let's make this understandable.0:35
  11. First of all, let's add colors to the jobs.0:38
  12. Now, let's illustrate the cells.0:41
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  1. The central color represents the main job of the cell, while the surrounding ones represent secondary duties.0:43
  2. Now, the immune system looks like this.0:49
  3. Now, the interactions.0:52
  4. Isn't this complexity just awesome?0:54
  5. For this video, we will only talk about these cells and ignore the rest.0:56
  6. So what happens in the case of an infection?1:03
  7. It's a beautiful day when suddenly a wild rusty nail appears and you cut yourself.1:12
  8. The first barrier of the immune system is breached, your skin.1:18
  9. Nearby bacteria seize on the opportunity and enter your wound.1:22
  10. They start using up the body's resources and double their numbers about every 20 minutes.1:25
  11. At first, they fly under the radar, but when a certain bacteria population is reached, they change their behavior and start to damage the body by changing the environment around1:31
  12. them.1:39
  13. The immune system has to stop them as fast as possible.1:40
  14. First of all, your guard cells, known as macrophages, intervene.1:44
  15. They are huge cells that guard every border region of the body.1:48
  16. Most of the time, they alone can suffocate an attack because they can devour up to 100 intruders each.1:52
  17. They swallow the intruder whole and trap it inside a membrane.1:58
  18. Then the enemy gets broken down by enzymes and is killed.2:01
  19. On top of that, they cause inflammation by ordering the blood vessels to release water into the battlefield, so fighting becomes easier.2:05
  20. You notice this as a very mild swelling.2:12
  21. When the macrophages fight for too long, they call in heavy backup by releasing messenger proteins that communicate location and urgency.2:14
  22. Neutrophiles leave their patrol routes in the blood and move to the battlefield.2:22
  23. The neutrophiles fight so furiously that they kill healthy cells in the process.2:27
  24. On top of that, they generate barriers that trap and kill the bacteria.2:31
  25. They are indeed so deadly that they evolved to commit suicide after five days to prevent them from causing too much damage.2:35
  26. If this is not enough to stop the invasion, the brain of the immune system kicks in.2:42
  27. The dendritic cell gets active.2:46
  28. It reacts to the signals of the soldiers and starts collecting samples from the enemies.2:49
  29. They rip them into pieces and present the parts on their outer layer.2:53
  30. Now, the dendritic cell makes a crucial decision.2:57
  31. Should they call for antivirus forces that eradicate infected body cells or an army of bacteria killers?3:00
  32. In this case, antibacteria forces are necessary.3:06
  33. It then travels to the closest lymph node in about a day.3:09
  34. Here, billions of helper and killer T -cells are waiting to be activated.3:12
  35. When T -cells are born, they go through a difficult and complicated training process and only a quarter survives.3:17
  36. The surviving cells are equipped with a specific setup.3:23
  37. And the dendritic cell is on its way looking for a helper T -cell with a setup that's just right.3:26
  38. It's looking for a helper T -cell that combined to the parts of the intruders which the dendritic cell has presented on its membrane.3:32
  39. When it finally finds one, the chain reaction takes place.3:38
  40. The helper T -cell is activated.3:41
  41. It quickly duplicates thousands of times.3:44
  42. Some become memory T -cells that stay in the lymph node and will make you practically immune against this enemy.3:47
  43. Some travel to the field of battle to help out.3:52
  44. And the third group goes on to travel to the center of the lymph node to activate a very powerful weapons factory.3:54
  45. Like the T -cells, they're born with a specific setup.4:00
  46. And when a B -cell and a T -cell with the same setup meet, hell breaks loose.4:03
  47. The B -cell duplicates rapidly and starts producing millions of little weapons.4:07
  48. They work so hard that they would literally die from exhaustion very fast.4:12
  49. Here, helper T -cells play another important role.4:17
  50. They stimulate the hardworking factories and tell them, don't die yet, we still need you.4:20
  51. Keep going.4:24
  52. This also ensures that the factories die if the infection is over so the body doesn't waste energy or hurt itself.4:26
  53. But what is produced by the B -cells?4:32
  54. You've heard of them, of course, antibodies.4:34
  55. Little proteins that are engineered to bind to the surface of the specific intruder.4:37
  56. There are even different kinds of antibodies that have slightly different jobs.4:42
  57. The helper T -cells tell the plasma cells which type is needed the most in this particular invasion.4:46
  58. Millions of them flood the blood and saturate the body.4:51
  59. Meanwhile, at the site of infection, the situation is getting dire.4:55
  60. The intruders have multiplied in number and start hurting the body.4:59
  61. Guard and attack cells fight hard but also die in the process.5:03
  62. Helper T -cells support them by ordering them to be more aggressive and to stay alive longer.5:07
  63. But without help, they can't overwhelm the bacteria.5:12
  64. But now the second line of defense arrives.5:15
  65. Billions of antibodies flood the battlefield and disable lots of the intruders rendering them helpless or killing them in the process.5:18
  66. They also stun the bacteria and make them an easy target.5:25
  67. Their back is built to connect to killer cells so they can connect and kill the enemy more easily.5:28
  68. Macrophages are especially good at gnoming up the bacteria which antibodies have attached to.5:34
  69. Now the balance shifts.5:39
  70. In a team effort, the infection is wiped out.5:41
  71. At this point, millions of body cells have already died.5:44
  72. No big deal, the losses are quickly replenished.5:48
  73. Most immune cells are now useless and without the constant signals they commit suicide so as not to waste any resources.5:51
  74. But some stay behind, the memory cells.5:59
  75. If this enemy is encountered ever again in the future, they will be ready for it and probably kill it before you even notice.6:02
  76. This was a very, very simplified explanation of parts of the immune system at work.6:09
  77. Can you imagine how complex this system is?6:14
  78. Even at this level when we ignore so many players and all the chemistry.6:16
  79. Life is awfully complicated, but if we take the time to understand it we always encounter endless wonders and great beauty.6:20
  80. This bird has magical powers.6:30
  81. Let's see a demonstration.6:33
  82. Bring in the latest scientific research.6:35
  83. Wow, that's a lot of complicated stuff about the immune system and all its cells.6:38
  84. How could someone possibly understand all of this?6:43
  85. Incredible!6:46
  86. This overview is delightful and easy to grasp, but still scientifically accurate.6:47
  87. Let's make it a bit more difficult.6:52
  88. Can she make all of evolution visible at a glance?6:55
  89. This is brilliant.6:59
  90. You can clearly see the relationships between species and how they evolved.7:01
  91. And look at those illustrations.7:05
  92. These posters are ready to be shared with the world.7:07
  93. These very special pieces of Kotzkart are now available on our shop along with many other science products all researched with care and created with love by the burbs with7:11
  94. magical powers.7:20
  95. Every Kotzkart product you buy directly funds another moment we get to spend working on our videos.7:21
  96. Thank you so much for being a part of our story and for making this channel possible.7:28

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burbs, communicators, simplified, duplicates, furiously, overview
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