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October 20, 2022 - January 9, 2023
Your immune system is “aware” that there are very different kinds of pathogens, that all require very different responses to get rid of them.
Bacteria are among the oldest living things on this planet and have been partying for billions of years. They are the smallest things we can consider alive
bacteria have at least ten times more mass than all animals combined.
In a pleasant environment, a single bacterium can reproduce once every twenty to thirty minutes by dividing into two bacteria. So after four more hours of dividing, there would already be 8,000 of them. A few more hours and there would be millions. And in a few more days, there would be enough bacteria to fill up the entirety of the world’s oceans.
So our bodies had to arrange with this fact of life and make the best of it. A life without bacteria is impossible.
The life of your skin cells begins around one millimeter deep. Here, the Skin Industrial Complex is situated. In the basal layer, stem cells do nothing but calmly multiply.
your skin cells mature, they develop long spikes and interlock with the other cells around them to form a dense and impassable wall. Next your skin cells begin manufacturing lamellar bodies, tiny bags that squirt out fat to create a waterproof and impermeable coat that covers the cells and the little bit of space that is left between them.
it is filled with natural antibiotics called defensins
Up to fifty layers of dead cells, fused together on top of each other, form the dead part of your skin that ideally covers your whole body.
Depending on your age, it takes your skin between thirty and fifty days to completely turn over. Every single second, you shed around 40,000 dead skin cells.
sweat contains even more natural antibiotics that can passively kill microbes.
the acid mantle, which is a mixture of sweat and other substances secreted by glands below your skin. The acid mantle is not so harsh that it would hurt you, it just means that the pH of your skin is slightly low and therefore slightly acidic and that is something a lot of microorganisms don’t like.
The acid mantle has another great passive effect mostly geared towards bacteria: The inside and outside of your body have different pH levels.
A healthy individual’s skin holds up to forty different bacteria species, as different areas of your skin are drastically different environments with their own specific climates and temperatures.
Overall, an average square centimeter of your skin is home to around a million bacteria. About ten billion friendly bacteria in total populate your outsides right now.
Your skin microbiome is pretty happy with its environment and does not intend to share it with strangers.
Going even further, it seems that they are even able to regulate the immune cells below the skin and tell it which harmful substances they should produce and in what quantities.
Scientists don’t completely understand yet how this deal is made, how the immune system decides who is allowed to settle, or how the bacteria educate the immune system about their intentions.
the way the skin is built, it is practically immune against viruses. Because these little parasites can infect only living cells and the surface of your skin consists only of dead cells, there is nothing to infect here!
pH is short for POWER OF HYDROGEN,
POWER OF HYDROGEN is a scale that describes how many hydrogen ions are present in a water-based solution.
This is “math power,” correctly called exponential. So going up 1 POWER on the pH scale means having ten times fewer hydrogen ions.
A lot of hydrogen ions means that something is acidic:
Macrophages and they are the largest immune cells your body has to offer.
Macrophages are able to stretch out parts of themselves,
Neutrophils have heard the cries for help and smelled the signs of death and begun to move. At the site of infection they leave the rushing ocean of the blood and enter the battlefield. Just like the Macrophages, the panic and alarm signals activated them, turning them from pretty chill fellows into killing frenzied maniacs.
Neutrophils are on a tight timer: Once active they only have hours before they will die of exhaustion as their weapons do not regenerate. So they make the best of the situation and use them freely—not only killing enemies but also causing real damage to the tissue they should be protecting in principle.
of them explode, casting wide and toxic nets around themselves in the process. These nets are spiked with dangerous chemicals that seal off the battlefield, trap and kill bacteria, and make it harder for them to leave and hide.
The cells fighting at the site of infection started a crucial defense process: Inflammation. This means they ordered your blood vessels to open up and let warm fluid stream into the battlefield, like a dam opening up towards a valley. This does a few things: For one, it stimulates and squeezes nerve cells that are deeply unhappy about their situation and send pain signals to the brain, which makes the human aware that something is wrong and an injury occurred.
Among the intruders there is a pathogen. A soil bacteria that is actually able to deal with the immune response and to multiply quickly.
The Dendritic Cell, the mighty messenger and intelligence officer of the Innate Immune System
they prepared samples made from the dead intruders, to present their findings to the intelligence centers of the immune system.
It takes the Dendritic Cell about a day to reach its destination and when it finds what, or better, who it is looking for, a beast will rouse from its sleep and all hell will break loose.
Platelets are not actually cells but cell fragments from another cell called megakaryocyte. Enormously large fellows, that are around six times larger than your average cell and live in your bone marrow.
When one of these weird arms has grown enough, small packages break off. Functional mini parts of cells that are carried away by the blood. These packages are your platelets and every time you cut yourself or suffer a wound, they close it. A single megakaryocyte produces around 10,000 of these platelets
Macrophages and Neutrophils are the damage dealers of the Immune system. Together they are a special class of cells called phagocytes
When a phagocyte, like a Macrophage, wants to swallow an enemy, it reaches out to it and grabs it tightly. Once it has a firm grip, it pulls its victim in, folds a part of its membrane into itself, and engulfs the victim, trapping it in a sort of mini prison
dissolving it into its components, into amino acids, sugars, and fats that are not only harmless, but even useful.
one of the main jobs of Macrophages is to eat and swallow stuff that the body does not want around, battle or not.
every second of your life, around one million of your cells die by controlled cell suicide, called apoptosis
Macrophages, attracted by the signals, pick up the shreds of the former cells and recycle the parts.
Macrophages live up to several months. Billions of them hang out just below your skin,
In your liver and spleen, they catch old blood cells and eat them whole to recycle the valuable iron they carry.
An activated angry Macrophage can swallow up to 100 bacteria before it dies of exhaustion.
when an infection has been dealt with, Macrophages actually can slow or even shut down the immune response at the site of battle to prevent further damage.
The Neutrophil is a bit of a simpler fellow.
a chimp on coke with a bad temper and a machine gun.
is by far the most abundant immune cell in your blood and easily one of the most potent. Neutrophils are indeed so dangerous that they come with a kill switch. They are on a tight timer and only live a few days when they are not needed before they commit controlled suicide.
And so every single day 100 billion Neutrophils give up their lives voluntarily and die. And every single day around 100 billion more are born, ready to fight for you if necessary.
They can throw acid at enemies and kill themselves to create deadly traps.
