How The Immune System ACTUALLY Works – IMMUNE

Summary

This script delves into the intricate workings of the human immune system, likened to a vast army protecting the body from invaders. It narrates the battle that ensues when the body is wounded, detailing the roles of macrophages, neutrophils, and the adaptive immune response involving T and B cells. The script paints a vivid picture of the body's defense mechanisms, from the first line of defense to the formation of memory cells, illustrating the complexity and marvel of our biological defenses.

Takeaways

• 🧠 The human immune system is the second most complex biological system after the brain, yet it's often misunderstood.
• 🛡️ The immune system consists of various organs, including two large ones, and a transport network for rapid response to threats.
• 💥 It produces hundreds of billions of fresh cells daily, organized like an army with diverse roles, including soldiers and suicide bombers.
• 🛑 The immune response begins with chemical alarm signals from damaged cells, alerting the immune system to an invasion.
• 🦏 Macrophages are the first responders, large cells that engulf and digest up to 100 bacteria before exhaustion.
• 💣 Neutrophils are suicide warriors that release deadly chemicals and can even explode to trap and kill bacteria.
• 🩸 Inflammation is a sign of the immune system's battle, with blood vessels releasing fluid into the affected area.
• 🔍 Dendritic cells act as intelligence officers, collecting samples of invaders to find the right T cells for a targeted response.
• 🔑 Helper T cells are activated by dendritic cells and play a crucial role in activating other immune cells for a specific response.
• 🧬 The immune system has a vast array of unique helper T cells and B cells, each capable of combating a wide range of pathogens.
• 🛡️ B cells produce antibodies that neutralize bacteria, and memory cells ensure long-term immunity against specific threats.
• 📚 The book 'Immune: A Journey into the Mysterious System That Keeps You Alive' by Philipp Dettmer offers a detailed exploration of the immune system.

Q & A

What is the human immune system and why is it considered complex?

The human immune system is a complex biological system that protects the body from billions of microorganisms and perverted cells that can turn into cancer. It is considered complex due to its multitude of organs, transport networks, and the vast number of cells it coordinates to maintain health.

What are the first cells to respond to an invasion in the body?

The first cells to respond to an invasion are macrophages, which are large cells that can engulf and digest up to 100 bacteria before they become exhausted.

How do neutrophils contribute to the immune response?

Neutrophils are intense suicide warriors that live only to kill invaders. They vomit deadly chemicals at bacteria, devour them, and can even explode, casting a toxic net from their own DNA to trap and kill bacteria.

What is the role of the complement proteins in the immune system?

Complement proteins are a sort of automated liquid weapon that enters the battlefield during an immune response. They stun and kill bacteria by ripping holes into them.

What happens when the first line of defense is unable to handle the invaders?

If the first line of defense is overwhelmed, the dendritic cells, acting as intelligence officers, collect samples of the invaders and present them to helper T cells, which then activate the second line of defense.

How does the immune system have a weapon against every possible disease?

The immune system has billions of unique helper T cells, each with the potential to recognize and respond to a specific pathogen. This diversity allows it to combat a wide range of diseases.

What is the function of helper T cells in the immune response?

Activated helper T cells clone themselves and split into two groups. One group supports the existing immune cells, like macrophages, by reinvigorating them, while the other group activates B cells to produce antibodies.

What are antibodies and how do they assist in the immune response?

Antibodies are protein super weapons that resemble tiny crabs with pincers to grab enemies. They are produced by B cells and help by clumping bacteria together, making them unable to move or fight, and facilitating their destruction by other immune cells.

What is the significance of memory cells in the immune system?

Memory cells are helper T cells that remain after an immune response. They guard the tissue for years, ensuring that the same bacteria will not be able to invade again, providing long-term immunity.

How does the book 'Immune: A Journey into the Mysterious System That Keeps You Alive' relate to the script?

The book, written by Philipp Dettmer, provides a deep dive into the immune system, explaining its vastness and complexity. It aims to change how readers think about their bodies and offers insights into how the immune system fights various diseases.

Why is pre-ordering the book important and what assurance does the author provide?

Pre-ordering is crucial in the book industry as it helps gauge demand and support the author. The author assures that the book is finished and will not require any patches or updates post-publication.

Outlines

00:00

🛡️ The Human Immune System's First Line of Defense

The human immune system is a complex biological marvel, second only to the brain in complexity. It comprises various organs and a transport network, constantly producing new cells to protect the body from harmful microorganisms and cancerous cells. The video script describes the initial response to an injury, where the body's first line of defense is activated. Macrophages and neutrophils are the first responders, engaging in a battle against invading bacteria. Macrophages engulf and digest bacteria, while neutrophils release toxic chemicals and can even explode to trap and kill bacteria. This process results in inflammation, a visible sign of the body's internal struggle.

05:01

🔬 The Role of Dendritic and Helper T Cells in Immune Response

The script delves into the role of dendritic cells as intelligence officers of the immune system. These cells collect samples from invaders and present them to helper T cells, which serve as commanders within the immune response. Upon finding a matching T cell, the dendritic cell activates it, initiating a more specific and potent defense. Helper T cells then clone themselves and split into two groups: one to energize and refocus macrophages, and the other to activate B cells, which produce antibodies tailored to the specific threat. This process highlights the immune system's remarkable ability to recognize and combat a vast array of pathogens.

10:03

📚 The Immune System's Memory and Philipp Dettmer's Book 'Immune'

The final paragraph explains the immune system's memory, where some T and B cells remain after an infection to provide long-term protection. Memory cells ensure that the same bacteria cannot easily invade again, while B cells continue to produce a small amount of antibodies. The paragraph also introduces 'Immune: A Journey into the Mysterious System That Keeps You Alive,' a book by Philipp Dettmer that offers an in-depth exploration of the immune system. The book aims to educate readers about this vital system in an engaging and accessible manner, encouraging pre-orders to support the author's decade-long passion project.

Keywords

💡Immune System

The immune system is a complex biological network that defends the body against disease-causing microorganisms and harmful substances. In the video, it is likened to an army with various roles such as soldiers, captains, and intelligence officers, highlighting its multifaceted nature in protecting the body from invaders like bacteria and its own cancerous cells.

💡Macrophages

Macrophages are large white blood cells that act as the first line of defense in the immune system. They engulf and digest foreign particles, dead cells, and pathogens. The script describes them as 'stoic cells' that can consume up to 100 bacteria before exhaustion, emphasizing their role in immediate response to infection.

💡Neutrophils

Neutrophils are another type of white blood cell, characterized as 'intense suicide warriors' in the script. They are short-lived and are dedicated to the cause of destroying pathogens, often at the cost of their own life, as seen when they 'vomit deadly chemicals' or even explode to trap and kill bacteria.

💡Inflammation

Inflammation is the body's response to injury or infection, marked by redness, heat, swelling, and pain. The script uses the metaphor of a dam opening to describe the influx of fluid into the injury site, which is a visible sign of the ongoing battle between the immune system and invading pathogens.

💡Complement Proteins

Complement proteins are part of the immune system's second line of defense. They are described as 'automated liquid weapons' in the script, capable of killing bacteria by creating holes in their cell walls. This illustrates their critical role in the immune response.

💡Dendritic Cells

Dendritic cells are antigen-presenting cells that act as the 'intelligence officers' of the immune system. They collect samples of pathogens and present these to T cells, as depicted in the script where the dendritic cell 'rubs itself against every helper T cell it meets' to find the right one to activate.

💡Helper T Cells

Helper T cells are a type of T lymphocyte that play a central role in the immune response by activating other immune cells. The script describes them as 'all-purpose commander cells' that, once activated, can clone themselves and help coordinate the immune response against specific pathogens.

💡B Cells

B cells, or B lymphocytes, are responsible for producing antibodies, which are proteins that identify and neutralize foreign objects such as bacteria and viruses. The script refers to them as 'antibody factories' that can produce 'up to 2,000 antibodies per second' once activated.

💡Antibodies

Antibodies are Y-shaped proteins that bind to antigens on the surface of pathogens, marking them for destruction by other immune cells. In the script, they are likened to 'tiny crabs with two pincers' that grab and immobilize bacteria, illustrating their function in the immune response.

💡Memory Cells

Memory cells are a type of T or B cell that remain in the body after an infection has been cleared. They remember the pathogen and provide a faster and more effective response if the same pathogen is encountered again. The script mentions that 'a few helper T cells remain and turn into memory cells' to guard the tissue.

💡Immune Response

The immune response is the body's reaction to the presence of pathogens or foreign substances. The script outlines the stages of this response, from the initial attack by macrophages and neutrophils to the activation of T and B cells, and the eventual production of antibodies and memory cells, showcasing the coordinated effort of the immune system.

Highlights

The human immune system is the second most complex biological system after the human brain.

The immune system consists of hundreds of tiny organs, two large organs, and its own transport network.

It produces hundreds of billions of fresh cells daily, organized like an army with various roles.

The immune system protects the body from microorganisms and cancerous cells.

The first line of defense includes macrophages, large cells that engulf and digest bacteria.

Macrophages can consume up to 100 bacteria before exhaustion.

Neutrophils are suicide warriors that live to kill bacteria, even at the cost of their own cells.

Neutrophils can explode, releasing a toxic net to trap and kill bacteria.

Inflammation is a sign of the immune response, with fluid streaming into the affected area.

Complement proteins are liquid weapons that kill bacteria by creating holes in their cell walls.

Dendritic cells act as intelligence officers, collecting samples of bacteria for immune response.

Helper T cells are activated by dendritic cells and initiate a specific immune response.

The immune system has billions of unique helper T cells with weapons against every possible enemy.

Activated helper T cells clone and split into groups to aid macrophages and activate B cells.

B cells produce antibodies, protein super weapons that immobilize bacteria for destruction.

Memory cells remain to guard against future infections by the same bacteria.

The book 'Immune: A Journey into the Mysterious System That Keeps You Alive' provides a deep dive into the immune system.

Pre-ordering the book is crucial in the publishing industry and ensures its completion.

Transcripts

The human immune system is the most complex biological system we know, after the human brain,

and yet most of us never learn how it works.

Or, what it is.

Your immune system consists of hundreds of tiny—and two large—organs.

It has its own transport network spread throughout your body.

Every day, it makes hundreds of billions of fresh cells organized like an army.

With soldiers, captains, intelligence officers, heavy weapons, and crazy suicide bombers.

It's not some sort of abstract entity.

Your immune system is you.

Your biology protecting you from the billions of microorganisms that want to consume you,

and from your own perverted cells that turn into cancer.

It's so manifold that it's impossible to cover in one video,

so we'll make a series looking at different aspects of it.

Today: What happens when your body is invaded

and your first lines of defenses are engaged in a fight for life and death.

It's been a normal day,

when suddenly the world explodes and an asteroid rips the sky open.

Countless alien life forms invade,

ready to destroy cities and infrastructure, and eat civilians...

Or, this is what your cells experience.

You look at your bleeding thumb that you just cut on a dirty twig in the park.

How annoying!

But inside the wound, a horrible catastrophe has happened.

There are dead cells, and blood and dirt everywhere.

Even worse, countless bacteria invade the warm caverns between your helpless cells

to explore their new home, steal your resources, and poop everywhere.

Immediately, the first stage of your defense kicks in.

The cells that survive the impact, or are hurt or dying, scream in panic

releasing an onslaught of chemical alarm signals that awaken your immune system.

The first cells to show up are macrophages.

If an average cell were the size of a human, a macrophage would be the size of a black rhino.

A stoic cell in principle but you wouldn't want to annoy it.

Bacteria -do- annoy them.

Within seconds, the large cells attack and begin killing them without mercy.

They stretch out parts like the arms of an octopus,

and grab the bacteria to swallow them whole and digest them alive.

A macrophage can eat 100 bacteria before it's exhausted.

But there are too many enemies, so the macrophages call for reinforcements.

In your blood, hundreds of thousands of neutrophils pick up their signals and move to the battlefield.

Neutrophils are intense suicide warriors that only live to kill.

They're so enthusiastic about killing that they kill themselves a few days after birth,

so they don't have time to accidentally destroy your body from the inside.

As soon as neutrophils arrive, they begin vomiting deadly chemicals at bacteria, or devour them.

They are so careless in their attacks that they are causing real damage to your own cells.

But collateral damage is not their concern now,

or ever.

Some neutrophils go so far to push their suicide button and explode,

casting a wide and toxic net made from their own DNA filled with deadly chemicals that trap and kill bacteria.

Sometimes, they can continue fighting after that, even though they're sort of dead already.

This is how much fun they have killing!

While the battle rages, your blood vessels let fluid stream into the battlefield like a dam opening up towards a valley.

You notice this as inflammation.

Your thumb swells up a little and gets red and warm.

The fluid brings a silent killer into the battle zone, millions of complement proteins.

A sort of automated liquid weapon that stuns and kills bacteria by ripping holes into them.

We made a whole video explaining them in detail.

We are reaching a crossroad now.

If things go well, your first line of defense kills the invaders quickly.

But sometimes, the enemies are too strong and would overwhelm your defenses eventually,

which means certain death for you, the human.

This is the hour of the dendritic cell, your immune system's intelligence officer.

While your soldiers were bashing in heads,

it was collecting samples by ripping bacteria into tiny parts and covering itself in it.

Like a soldier decorating itself in the guts of a dead enemy.

The cell leaves the battlefield and enters the superhighway of your immune system

that connects all your tissues with your immune headquarters.

Your lymph nodes.

The dendritic cell coming from the battlefield is looking for a helper T cell,

which is a sort of all-purpose commander cell within your immune army.

But not any helper T cell.

One that happens to have just the right weapon for the bacteria that infected your wound.

So it goes around and rubs itself, still covered in bacteria parts, against every helper T cell it meets.

Most T cells are a bit disgusted and not interested.

But after a few hours, something clicks.

A helper T cell recognizes the bacteria parts.

This cell is the weapon that's needed right now.

The dendritic cell is overjoyed and activates the helper T cell.

Okay, wait.

How come your immune system has a cell that has a weapon against the specific bacteria that infected you?

Well, your immune system has a perfect weapon against every possible disease in the universe.

Against the Black Death, the Coronavirus, or an infection that will emerge in 100 years on Mars.

We'll talk about this a bit more in the next video because it's very complex.

So, for now, just know that you have billions of unique helper T cells

that each have weapons against every possible enemy.

After the right T cell is activated, your second line of defense awakes

and rises like a teenager that needs to get up on a school day...

Very slowly.

Your heavy weapons are incredibly effective but they're not fast.

The activated helper T cell begins to clone itself over and over again.

One becomes two, two become four, until there are thousands of them.

Now, they split into two groups.

The first group quickly moves to help out your soldiers.

At the battlefield, things are getting out of hand.

A tired macrophage is ready to give up.

After fighting for days, it just wants to go to sleep like many of its buddies have done already.

But now the helper T cells arrive.

One of them comes to the tired macrophage and whispers something using special chemical signals.

In a heartbeat, the demoralized soldier feels fresh again.

But there's something else.

A hot white anger.

The macrophage knows what it needs to do...

Kill.

Invigorated, it throws itself against the enemies once again.

All over the battlefield, this begins to happen.

Meanwhile, the second group of helper T cells was working on activating another line of defense:

B cells, your antibody factories.

Antibodies are protein super weapons that look like tiny crabs with two pincers to grab enemies.

Just like the helper T cells, there are B cells in your body

that are able to make just the right antibodies for every possible enemy.

And the helper T cell is looking for exactly these B cells.

After a day or two, the right B cell is found, and begins to clone itself.

As soon as enough clones have been made,

each B cell begins pumping out up to 2,000 antibodies per second!

About a week after you injured yourself and bacteria invaded,

your second line of defense finally arrives in full force.

The tiny army begins to saturate the battlefield, pinching and stunning desperate bacteria.

The antibodies clump them together and make them unable to move or fight,

while your soldiers massacre the defenseless victims.

The tide is turning fast.

As the last enemies are cleaned up, your soldiers realize they are no longer needed,

and begin to kill themselves to save resources.

But not all of them.

A few helper T cells remain and turn into memory cells.

They will guard the tissue for years,

making sure the same bacteria will never again gain a foothold here.

Similarly, a few B cells will stay alive

and keep producing a low amount of antibodies,

making you immune against this bacteria,

maybe for the rest of your life.

One day you wake up and notice that the wound has grown over

and left nothing but a faint red mark.

You were completely unaware of the drama your cells had to deal with.

For you, the whole ordeal was a slight annoyance.

While for millions of cells, it was a desperate fight for life and death.

But this is just the beginning of the epic story that unfolds inside you every day,

and is told in full in

"Immune: A Journey into the Mysterious System That Keeps You Alive",

written by Philipp Dettmer, the founder and head writer of Kurzgesagt.

The book is a beautifully illustrated deep dive into the immune system,

the most important thing you don't know enough about,

that will forever change how you think about your body.

Written to be as simple and fun as possible,

it's been an ongoing passion project for almost a decade

because the immune system is just about the most amazing and fascinating topic there is.

So, go on a journey and get to know your own body.

From mystery organs, murder universities, to the largest library in the universe.

Explore how incredibly vast your immune system is and how it actually works.

How it fights enemies from cancer to HIV, or just the flu.

Learn how you can boost it and if that's actually a good idea.

The book will be out in six weeks

and it would mean the world to us and Philipp if you could pre-order it.

Pre-ordering is super important in the world of books,

and in contrast to games, we can guarantee that it's actually finished

and there will be no day one patch.

There's a link in the description.

This is the end of a decade-long personal journey and we'd love to see what you think.

Thank you for watching.