The Immune System: It’s you against the world!
Let’s say you are strolling through the park on a Sunday afternoon, knowing that nothing can ruin your day. Suddenly, you fall and cut your skin. “Aw shoot! I was just having a perfect day,” you say. You go home, feeling annoyed. But on the inside of you, it’s horrible. There’s blood, dirt, and bacteria everywhere! Let’s take one bacteria, named Bacteria Boy, and look at what’s happening through his eyes.
First, Bacteria Boy enters the body. He explores his new environment, and likes it. There are tons of host cells for Bacteria Boy to feed on! So he rushes over to the closest cell, and started to chew away. After he finishes his meal, Bacteria Boy goes over to another host cell and starts eating. The cells that are still alive start to send signals to ignite the immune system. And this is where the action begins.
Our cells are in trouble. Someone needs to kill Bacteria Boy, and fast! So the first one to step up is… The Great Macrophage! The Macrophages are huge, at least compared to an average cell. If the average cell were the size of a human, a macrophage would at least be the size of a rhino! What do the macrophages do, though?
Bacteria Boy and his tribe soon find out. He marches in with hundreds of friends, and tries to destroy the body. But the macrophages go, “Nuh-uh! You ain’t goin’ any further than here.” Of course, in real life, they don’t say that, but for the sake of fun, let’s assume a nasty conversation was getting started. “You wanna bet?” Bacteria Boy and the tribe say. “CHARGE!”
Before we jump in, how do the cells of our body recognize other friendly cells, and enemy cells? This is because of the basic building blocks of life:
PROTEINS.
Cells from the body check other cells to feel for their proteins. If they recognize the proteins, great! It’s a body cell. Otherwise, it must be an invader.
Getting back on topic, the macrophages are made to kill. They are microscopic warriors that will devour invaders whenever given the chance. So they accept the battle and fight Bacteria Boy and his army. They start eating up the bacteria that are in the body. But cells don’t have mouths, right? So how do they “eat” intruders? Basically, they press the bacteria to their skin, and it goes in. The granules (aka little deadly dots of doom) break down the bacteria. But soon, the Macrophages get exhausted, and go to sleep. But your immune system hasn’t given up yet!
Bacteria Boy and his tribe march on. But our body hasn’t lost! So it releases the Neutrophils; which are more or less living biological bombs that can obliterate bacteria. The neutrophils bounce onto the battlefield, looking for someone to sink their poisonous insides into. Finally, they spot Bacteria Boy, and get ready for anything. The neutrophils head for Bacteria Boy, and show their power.
Some violently explode, trapping all bacteria within their range and killing them. Other neutrophils sneak up on the bacteria and eat them up. Still others spit out enzymes to annihilate the intruders. But soon, even these death machines die off, and Bacteria Boy’s tribe heads for the more important parts of your body.
The neutrophils have given up. The macrophages are exhausted. But your immune system still has tons more in stock for Bacteria Boy’s army! A new immune cell pops onto the battlefield; the Dendritic Cell! It doesn’t have to do much… it just mashes a few bacteria together and covers itself in them. But his job isn’t over! He embarks on a one-day journey up the lymphatic system (aka the ‘highway’ of the immune system), and into what’s more or less a huge library of T-Cells!
Fun Fact: You are immune against every disease in the world, including the Bubonic Plague (aka the Black Death), Yellow Fever, Covid-19, and all future outbreaks that will ever occur in our world! No, seriously. You might want proof for this, and I’ll give it to you.
The answer lies in your DNA. The substance that makes you, well, you! Every one of your cells contains DNA, even immunity cells. Your T-cells also have DNA. Except, unlike all of the other cells, they have one special ability:
T-CELLS CAN CHANGE THEIR DNA CODE.
This fact enables that there is at least one T-cell for every disease. But back to the battle. The dendritic cell has entered the T-cell library, and shows the bacteria to each one of the T-cells. They present the antigen in a MHC class II molecule, which turns the Virgin T-cell into a T-cell. Most of the T-cells think this is gross, but one of them knows this bacteria, and is ready to fight it! 🧬
Alright, the dendritic cell has found the proper T-cell. You may think that now the T-cell jumps into action, but you couldn’t be further from the truth. Getting a T-cell to wake up is very hard for a dendritic cell! Finally, the T-cell has woken up! Now I shall proceed to tell the next few steps your body takes in a very overdramatic way for absolutely no good reason:
THE T-CELL HAS ARISEN FROM IT‘S DEEP SLUMBER, AND KNOWS WHAT IT HAS TO DO. IT MUST CLONE ITSELF THOUSANDS OF TIMES UNTIL IT IS READY TO TAKE THE ENEMY (Bacteria Boy) ON. ONLY ONCE IT HAS BEEN MULTIPLIED TENS OF THOUSANDS OF TIMES WILL IT PROCEED TO TAKE THE NEXT PROCEDURE…
The T-cells have cloned. Now, they split into two groups. Let’s call the groups Group A and B, for the sake of learning. Group A goes through the lymphatic system’s highway, and is very alarmed. It goes and wakes up an old warrior; The Macrophages! Once they are back in action, the other group, Group B, goes to find the B-lymphocytes, or B-cells. And once these antibody factories awaken, there’s no stopping your immune system.
A significant achievement has been accomplished! The T-lymphocytes have located the B-lymphocytes. These leukocytes are a perfect match! (I like big words and I cannot lie!) Like the T-cell, there are B-cells for every invader to ever come in your body. Each one can produce a unique kind of antibody. An antibody is a substance B-cells produce to cover and trap the bacteria so they can be devoured by the macrophages. Once they are activated by the T-cells, they start making many mighty murdering-machines. Antibodies! The antibodies latch onto Bacteria Boy’s friends, and the macrophages eat ’em up! Only a few bacteria are left, but it’s time for the final countdown.
Will Bacteria Boy die? Or will you? This final showdown between you and the bacteria will decide it all. If the bacteria defeat your antibodies and macrophages, then they’ve earned the right to eat away at all of your cells and live in your body. Otherwise, they don’t, and they die. You are very powerful, though, and so are your cells. So let’s assume that Bacteria Boy is running away from some macrophages, when he’s captured by the antibodies. He is gobbled up by the macrophages now! The last few intruders are cleaned up, and you have won yet again against these invaders.
Now comes the sad part. All of your macrophages, B-cells, antibodies, and T-cells that fought in this war will self-destruct to conserve the energy in your body. Though a few T-cells will stay behind and become memory cells, so that if this bacteria ever comes back, your body can react quicker.
But bacteria can mutate, and your memory cells cannot detect mutated cells. So there will always be a Part 2 of the amazing, astonishing, and awe-inspiring affray between you and bacteria. So stay tuned!
