Shadowing Practice: The Immune System Explained I – Bacteria Infection - Learn English Speaking with Video
Creating lesson...
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Every second of your life you are under attack.
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Billions of bacteria, viruses and fungi are trying to make you their home.
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So our bodies have developed a super complex little army with guards, soldiers, intelligence, weapons factories and communicators to protect you from, well, dying.
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For this video, let's assume the immune system has 12 different jobs.
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For example, kill enemies, communicate, etc. And it has 21 different cells and two protein forces.
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These cells have up to four different jobs.
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Let's assign them.
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Here are the interactions.
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Now let's make this understandable.
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First of all, let's add colors to the jobs.
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Now let's illustrate the cells.
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The central color represents the main job of the cell, while the surrounding ones represent secondary duties.
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Now the immune system looks like this.
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Now the interactions.
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Isn't this complexity just awesome?
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For this video we will only talk about these cells and ignore the rest.
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So what happens in the case of an infection?
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It's a beautiful day when suddenly a wild rusty nail appears and you cut yourself.
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The first barrier of the immune system is breached, your skin.
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Nearby bacteria seize on the opportunity and enter your wound.
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They start using up the body's resources and double their numbers about every 20 minutes.
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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 around them.
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The immune system has to stop them as fast as possible.
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First of all, your guard cells, known as macrophages, intervene.
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They are huge cells that guard every border region of the body.
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Most of the time, they alone can suffocate an attack, because they can devour up to 100 intruders each.
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They swallow the intruder hole and trap it inside a membrane.
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Then the enemy gets broken down by enzymes and is killed.
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On top of that they cause inflammation by ordering the blood vessels to release water into the battlefield so fighting becomes easier.
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You notice this as a very mild swelling.
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When the macrophages fight for too long they call in heavy backup by releasing messenger proteins that communicate location and urgency.
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Neutrophiles leave their patrol routes in the blood and move to the battlefield.
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The neutrophiles fight so furiously that they kill healthy cells in the process.
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On top of that, they generate barriers that trap and kill the bacteria.
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They are indeed so deadly that they evolved to commit suicide after five days to prevent them from causing too much damage.
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If this is not enough to stop the invasion, the brain of the immune system kicks in.
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The dendritic cell gets active.
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It reacts to the signals of the soldiers and starts collecting samples from the enemies.
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They rip them into pieces and present the parts on their outer layer.
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Now the dendritic cell makes a crucial decision.
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Should they call for antivirus forces that eradicate infected body cells or an army of bacteria killers?
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In this case, antibacterial forces are necessary.
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It then travels to the closest lymph node in about a day.
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Here billions of helper and killer T cells are waiting to be activated.
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When T cells are born, they go through a difficult and complicated training process, and only a quarter survives.
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The surviving cells are equipped with a specific setup.
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And the dendritic cell is on its way looking for a helper T cell with a setup that's just right.
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It's looking for a helper T cell
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that combines to the parts of the intruders which the dendritic cell has presented on its membrane.
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When it finally finds one, a chain reaction takes place.
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The helper T cell is activated.
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It quickly duplicates thousands of times.
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Some become memory two cells that stay in the lymph node and will make you practically immune against this enemy.
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Some travel to the field of battle to help out.
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And the third group goes on to travel to the center of the lymph node to activate a very powerful weapons factory.
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Like the T-cells, they're born with a specific setup, and when a B-cell and a T-cell with the same setup meet, hell breaks loose.
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The B-cell duplicates rapidly and starts producing millions of little weapons.
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They work so hard that they would literally die from exhaustion very fast.
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Here helper T cells play another important role.
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They stimulate the hard working factories and tell them don't die yet we still need you keep going.
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This also ensures that the factories die if the infection is over so the body doesn't waste energy or hurt itself.
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But what is produced by the B cells?
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You've heard of them of course antibodies.
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Little proteins that are engineered to bind to the surface of the specific intruder.
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There are even different kinds of antibodies that have slightly different jobs.
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The helper T cells tell the plasma cells which type is needed the most in this particular invasion.
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Millions of them flood the blood and saturate the body.
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Meanwhile, at the site of infection, the situation is getting dire.
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The intruders have multiplied in number and start hurting the body.
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Guard and attack cells fight hard, but also die in the process.
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Helper T cells support them by ordering them to be more aggressive and to stay alive longer.
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But without help, they can't overwhelm the bacteria.
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But now the second line of defense arrives.
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Billions of antibodies flood the battlefield and disable lots of the intruders, rendering them helpless or killing them in the process.
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They also stun the bacteria and make them an easy target.
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Their back is built to connect to killer cells so they can connect and kill the enemy more easily.
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are especially good at gnoming up the bacteria which antibodies have attached to.
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Now, the balance shifts.
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In a team effort, the infection is wiped out.
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At this point, millions of body cells have already died.
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No big deal, the losses are quickly replenished.
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Most immune cells are now useless and without the constant signals they commit suicide, so as not to waste any resources.
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But some stay behind, the memory cells.
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If this enemy is encountered ever again in the future, they will be ready for it and probably kill it before you even notice.
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This was a very, very simplified explanation of parts of the immune system at work.
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Can you Can you imagine how complex this system is?
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Even at this level, when we ignore so many players and all the chemistry.
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Life is awfully complicated, but if we take the time to understand it, we always encounter endless wonders and great beauty.
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This bird has magical powers.
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Let's see a demonstration.
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Bring in the latest scientific research.
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Wow, that's a lot of complicated stuff about the immune system and all its cells.
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How could someone possibly understand all of this?
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Incredible!
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This overview is delightful and easy to grasp, but still scientifically accurate.
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Let's make it a bit more difficult.
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Can she make all of evolution visible at a glance?
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This is brilliant!
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You can clearly see the relationships between species and how they evolved.
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And look at those illustrations!
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These posters are ready to be shared with the world.
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These very special pieces of Kurzgesagt are now available on our
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shop along with many other sciencey products all researched with care and created with love by the Burbs with magical powers.
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Every Kurzgesagt product you buy directly funds another moment we get to spend working on our videos.
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Thank you so much for being a part of our story and for making this channel possible.
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Vocabulary and speaking notes for this lesson
This C1 speaking lesson is built on the video “The Immune System Explained I – Bacteria Infection”. The speaker keeps coming back to these words: cell, immune, bacteria, helper, intruder. This video has 105 sentences and 1286 words to shadow. The speech runs for 7:33. The speaker talks at a natural 170 words per minute, close to everyday conversation. Only 80% of the words are among the 3,000 most common in English, so the vocabulary is demanding.
Key vocabulary in this video
The 15 most advanced words in the video, with pronunciation and meaning:
| Word | Pronunciation | Meaning |
|---|---|---|
| bacterium noun | /bækˈtɪəɹ.ɪəm/ | A single-celled organism with cell walls but no nucleus or organelles. |
| helper noun | /ˈhɛlpɚ/ | One who helps; an aide; assistant; auxiliary. |
| intruder noun | /ənˈtɹudɚ/ | Someone who intrudes. |
| antibody noun | /ˈæn.tɪˌbɑ.di/ | A protein produced by B-lymphocytes that binds to a specific antigen. |
| dendritic adjective | /dɛndˈɹɪtɪk/ | Having a branching structure similar to a tree. |
| lymph noun | /lɪmf/ | A colourless, watery, coagulable bodily fluid which bathes the tissues and is carried by the lymphatic system into the bloodstream; it resembles blood plasma… |
| activate verb | /ˈæktɪˌveɪt/ | To encourage development or induce increased activity; to stimulate. |
| node noun | /noʊd/ | A knot, knob, protuberance or swelling. |
| battlefield noun | /ˈbætəlˌfiːld/ | The area where a land battle is fought, which may not necessarily be a field. |
| macrophage noun | /ˈmækɹɔʊː.feɪd͡ʒ/ | A white blood cell that phagocytizes necrotic cell debris and foreign material, including viruses, bacteria, and tattoo ink. It presents foreign antigens on… |
| neutrophile noun | /ˈnuː.tɹoʊ̯ˌfaɪ̯ɫ/ | Any organism that thrives in a relatively neutral pH. |
| duplicate verb | /ˈd(j)uː.plɪˌkeɪt/ | To make a copy of. |
| evolve verb | /ɪˈvɑlv/ | To move (something) in regular procession through a system. |
| membrane noun | /ˈmɛm.bɹeɪn/ | A mechanical, thin, flat flexible part that can deform or vibrate when excited by an external force. |
| antibacterial adjective | Killing or inhibiting bacteria. |
Phrasal verbs you will hear
| Word | Meaning |
|---|---|
| break down verb | To stop functioning. |
| go through verb | To travel from one end of something to the other. |
| help out verb | To provide assistance. |
| stay behind verb | To remain where one is, whilst others leave. |
| use up verb | To consume, deplete, expend, or exhaust. |
| wipe out verb | To destroy (especially, a large number or complete set of people or things); to obliterate. |
Sentences worth repeating
Short, complete lines from the video that you can reuse in everyday conversation:
- First of all, let's add colors to the jobs.
- Isn't this complexity just awesome?
- You've heard of them of course antibodies.
- Let's make it a bit more difficult.
Grammar in this video
The structures the speaker uses most, with the exact words from the video:
| Structure | In the video |
|---|---|
| Passive voice be + past participle — the focus is on what happens, not who does it | is breached · is reached · is killed |
| Present perfect have/has + past participle — a past action that still matters now | have developed · has presented · You've heard |
Pronunciation to watch
The speaker uses 6 contractions and reduced forms, such as can't, doesn't, don't. Say them the short way, as you hear them.
- The “sh” and “zh” sounds: replenish /ɹɪˈplɛn.ɪʃ/, inflammation /ɪnfləˈmeɪ̯ʃən/, illustration /ˌɪləsˈtɹeɪ̯ʃən/, demonstration /dɛmənˈstɹeɪʃən/
- Long words — get the stress right: antibody /ˈæn.tɪˌbɑ.di/, antivirus /ˈantɪvʌɪrəs/, communicator /kəˈmjuːnɪkeɪtə/, eradicate /əˈræd.əˌkeɪt/, furiously /ˈfjʊə̯ɹi.ə̯sli/
How to practise with this video
- Listen to the whole video once without speaking and note the words you do not know.
- Start at 0.75× speed, shadow it sentence by sentence, then go back to normal speed once it feels easy.
- Record yourself and compare with the original, paying attention to words like bacterium, helper, intruder.
What is the Shadowing Technique?
Shadowing is a science-backed language learning technique originally developed for professional interpreter training and popularized by polyglot Dr. Alexander Arguelles. The method is simple but powerful: you listen to native English audio and immediately repeat it out loud — like a shadow following the speaker with just a 1–2 second delay. Unlike passive listening or grammar drills, shadowing forces your brain and mouth muscles to simultaneously process and reproduce real speech patterns. Research shows it significantly improves pronunciation accuracy, intonation, rhythm, connected speech, listening comprehension, and speaking fluency — making it one of the most effective methods for IELTS Speaking preparation and real-world English communication.