Immune

Philipp Dettmer

14 annotations • Feb 2024 • data

Chapter 1

Even on the smallest scale, bacteria possess ways to defend against viruses, as they can't get taken over without a fight.
For example, many deaths from COVID-19 come from the immune system doing its job with too much enthusiasm.

Chapter 2

Your real weak points to infections are your mucous membranes—the surface that lines your windpipe and lungs, eyelids, mouth, and nose, your stomach and intestines, your reproductive tracts and bladder.

Chapter 3

Something alive separates itself from the universe around it. It has a metabolism, meaning it takes up nutrients from the outside and gets rid of internal garbage. It responds to stimuli. It grows and it can make more of itself. Cells do all these things.
In practice, proteins can't actually move that fast inside cells, because there are so many other molecules in the way. So they constantly collide and bump into the water molecules and other proteins in all directions. Everybody is pushing around and is getting pushed. This process is called Brownian motion and it describes the random movement of molecules in a gas or fluid. Which is the reason water is so important for your cells—because it enables other molecules to move around easily.
Cells are filled up by proteins. Proteins are three-dimensional puzzle pieces. Their specific shapes enable them to fit together or interact with other proteins in specific ways. Sequences of these interactions, called pathways, cause cells to do things. This is what we mean when we say that cells are protein robots guided by biochemistry. The complex interactions between dumb and dead proteins create a less dumb and less dead cell, and the complex interactions between slightly dumb cells create the pretty smart immune system.
Ants share a few properties with cells, most importantly: they are really dumb. This is not to be mean to ants. If you take a single ant and isolate it, it will just stumble around and be really useless, unable to do anything of value. But if you put a lot of ants together, they can exchange information and interact with each other and in unison do amazing things. Many ants construct complex structures with specialized areas like brood chambers, dedicated garbage places, or complex ventilation systems that control airflow. Ants automatically organize themselves into different classes and jobs, from foraging to defending or nursing.

Chapter 5

Your true enemies are an elite group that has found ways to overcome your defenses more effectively. Some even specialize in hunting humans, or are using you as a crucial part of their life cycle—enemies like the measles virus, for example, that have decided to be super annoying to us. Or Mycobacterium tuberculosis, which may have co-evolved with us as far back as 70,000 years ago and still kills about two million people each year. Others, like the novel coronavirus that causes the disease COVID-19, stumble onto us by accident and can't believe their luck.
Any sort of invader that is able to give your immune system a run for its money is called a Pathogen—which appropriately means "the maker of suffering."

Chapter 19

The Dendritic Cell is an antigen-presenting cell, which is a complicated way of saying: "covering yourself in your enemies' guts." Dendritic Cells literally disassemble pathogens into antigen-sized pieces and pack them into special contraptions on their membranes. On the human scale this would mean killing an enemy soldier and then covering yourself with bits and pieces of their muscles, organs, and bones so others could examine them.
For example, when the Black Death ravaged Europe in medieval times, there were people whose MHC class II molecules were just naturally really good at presenting the antigens of the bacterium Yersinia pestis, which caused the plague. They had a higher chance of surviving the disease and making sure humans as a species survived.
This is so incredibly crucial for our collective survival that evolution may have made it a contributing factor in mate selection. In human words: You find potential partners with MHC molecules that are different from yours more attractive! OK wait, what? How would you even know this? Well, you can literally smell the difference! The shape of your MHC molecules does influence a number of special molecules that are secreted by your body—which we pick up subconsciously, from the body odor of other people—so you communicate what type of immune system you have through your individual smell
In German there is even a popular saying "Jemanden gut riechen können," literally translated "being able to smell someone very well," which means "liking someone on an intuitive level."

Chapter 20

Some Helper T Cells become Memory Helper T Cells. Whenever you hear that you are immune to a disease, this is what this means. It means that you have living memory cells that remember a specific enemy.