Immune: A Journey Into the Mysterious System That Keeps You Alive

by Philipp Dettmer

The interactions of the parts of the immune system were too elegant and the dance they danced was too beautiful to stop learning about them.

the complex relationships of the many different actors of the immune system, with countless exceptions and unintuitive rules, are a challenge all by themselves. Immunology is hard even for the people working in public health, even for the people studying immunology, even for the foremost experts in the field. All of this makes the immune system horrible to explain. If you venture too far into simplification you deprive the learner of the beauty and wonder that lie in the evolutionary genius of the sheer endless complexity that deals with the most crucial problems of living beings. But if you include too much detail, it quickly becomes mind-numbingly hard to keep up with.

Health is really an abstract concept because it describes the absence of something. The absence of suffering and pain, the absence of limitations.

For a microorganism you are an ecosystem waiting to be conquered. An endless continent full of resources, breeding grounds, and opportunities to thrive, a really nice home. Arguably at some point they will succeed, as when you die, the decomposition of your body will be immensely sped up by an army of unhinged microbes no longer kept in check by your defenses.

An allergic shock shows strikingly how truly powerful your defense system is and how horribly it can go wrong: it may take a disease days to kill you—your immune system can do so in minutes.

If we took an honest look at what you are, you are, in a sense, nothing more than a complex tube. Granted, a tube that can close both ends. Also a lot wetter, slimier, and grosser.

Your cells are nothing but bags of proteins guided by chemistry. But together these proteins form a living being that can do a lot of really sophisticated things.

Its defining feature is that it is specific. Unbelievably specific, in fact. Your Adaptive Immune System “knows” every possible intruder. Its name, what it had for breakfast, its favorite color, its most intimate hopes and dreams.

When you look at yourself in the mirror, what you are really seeing is a very thin film of death covering your alive parts.

In the endless universe of the microworld there is nothing like an uninhabited space. Everything is free real estate, no matter how hostile it is.

For once, scientists gave something a great name: pH is short for POWER OF HYDROGEN, which is exciting and easy to remember. But then scientists decided to abbreviate it. Disappointing to say the least.

The Neutrophil is a bit of a simpler fellow. It exists to fight and to die for the collective. It is the crazy suicidal Spartan warrior of the immune system. Or if you want to stay in the animal kingdom, a chimp on coke with a bad temper and a machine gun.

While Macrophages are really great at breaking down bacteria and other cell garbage, they aren’t actually able to destroy the ink. So they just keep it inside themselves and store it. If you have a tattoo, when you look at it remember that it is partially trapped within your immune system. Unfortunately if a few years later you decide that the Chinese characters that turned out to mean “soup” are not as tasteful anymore and want to get them removed, your immune system also makes it really hard to get rid of a tattoo.

Another neat little detail about Neutrophils is that when they are chasing a pathogen, they often do so in swarms that follow the same mathematical rules as swarms of insects. So imagine being hunted by a bunch of hornets the size of cows and you get the same stressful experience that many bacteria must go through in the last few moments of their lives.

Besides, most places inside your body are pretty dark. If your insides are well lit, something has gone horribly wrong.

Well, welcome to the world of immunology, where words exist to make your life harder.

Their job is simply to get drunk. The Dendritic Cell is like a careful connoisseur of the fluids of your body that flows around between your cells. In a way, it treats them like expensive wine at an exclusive wine tasting event. It takes a sip, moves it around in its imaginary mouth to get the full picture of all its different tastes and components, and then spits it out again.

The lymph node megacities are like huge dating platforms where the Adaptive Immune System meets the Innate Immune System for hot dates. Or better, adaptive immune cells go and look for their ideal match. This is where the traveling Dendritic Cell arrives from the battlefield after about a day of chill travel.

Every time a B Cell receives a positive signal from a Helper T Cell, it begins a round of purposeful mutation. This process is called Somatic Hypermutation (also known as Affinity Maturation) and we will never use this clunky term again.

Again we see the principle of our two immune systems: The innate part does the actual fighting, but the adaptive part makes it more efficient with deadly precision.

Through the sheer incredible rate of reproduction and high numbers of individuals they produce in each reproductive cycle, with each infected cell, the chances that among a few thousand mutations, one is extremely beneficial and able to make a virus significantly better suited to survive is pretty high. It’s the old evolution, brute-force, throw-shit-at-the-wall-until-something-sticks approach. And it’s quite effective.*2

But when a Killer T Cell finds a cell that has virus antigen in its display window (MHC class I receptors) it immediately issues a special command to the cell: “Kill yourself but be very clean about it.” Not with aggression or anger, but matter-of-factly and with dignity, if you want to anthropomorphize this process.

the virus count drops harshly as thousands of Killer T Cells move through the battlefield, checking every cell they meet for infection, in a process that is called “serial killing.” Yes, this really is what it is called, praise where praise is due, immunologists nailed this term.

Hygiene is often confused with cleanliness—but you really should understand it as a targeted approach to remove potentially dangerous microorganisms from the key places and situations where they can make you sick.

While we obviously still have a long way to go and the modern world has a lot of downsides, the notion that “natural is better” is something only people who are not actually living in nature can say, and who have forgotten why our ancestors worked so hard to escape it.

Even the mere term “strong immune system” is a misnomer. Over everything else, you want a balanced immune system. Homeostasis. Aggression and calmness. You want elegant dancers who remember the choreography really well over pumped-up rugby players who want to smash stuff. In all likelihood, your immune system works exactly as intended.

Wherever the idea of your attitude affecting your cancer survival chances originally comes from, after decades of research it has become clear that with an extremely high certainty, your attitude has no effect on your chances of surviving cancer. Your immune system does not magically become better or worse at fighting cancer if you are or are not positive and happy. Still, this myth is going strong, as it appeals to our culture of self-empowerment and agency and is spread by many well-meaning people.

it is a terrible thing to say to someone with cancer that their attitude matters and that they should stay positive, because it does two things: For one, it puts the responsibility of healing and surviving on the sick person. It implies that if you don’t win the fight and have faced the gravest of all outcomes, it is your fault. That if you just had been more positive and optimistic, no matter how you really felt, that you could have saved yourself. Which is an incredibly unfair burden to put on someone who is fighting this disease.

As I’m writing this sentence the world has begun vaccinating against COVID-19 and with a bit of luck, as you are reading this sentence, we are all returning to a world that feels normal again.

But while space is nice and all, it has nothing over biology. Stars are dead clumps of burning plasma, and even the most complex and interesting one can’t compete with the wonder and complexity of the simplest bacteria trying to escape a Macrophage.

Despite these challenges, the immune system is one of the best topics to learn about because of the fact that it is so complex and made up of so many layers that all interact in such ingenious ways—it is like a window into the universe itself. A window into the complexity that surrounds you and that you are a part of.