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So you have an immune memory, and it is a living thing! Or many living things, as we introduced briefly before: Memory Cells.
After B Cells are activated through T Cells, some of them will turn into different kinds of Memory Cells! Living memory that will protect you for months, years,
The first group is called Long-Lived Plasma Cells
they constantly produce a moderate amount of Antibodies. So their entire job is to make sure that specific Antibodies against enemies we fought off in the past are always present in your bodily fluids.
there are also Memory B Cells.
For years and years they are inactive and just silently scan the lymph for the antigen they remember. If they ever catch an antigen they awake suddenly
This is the reason why you are immune forever
They are shortcuts that can activate your Adaptive Immune System in a heartbeat.
activated T Cells also produce Memory Cells, although with a few key differences. For one, after an infection is over, about 90% of all T Cells who fought at the site of the infection will kill themselves. The remaining 10% will turn into Tissue-Resident Memory T Cells, and become silent guardians.
there are Effector Memory T Cells.
they patrol the lymphatic system and your blood, not causing trouble, just looking for the antigen that once activated the cell that was their ancestor.
there are Central Memory T Cells, which remain stationary in your lymph nodes, doing nothing but keeping the memory of the attack. When activated they quickly pr...
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While measles was on its way to becoming the second human pathogen to be completely eradicated since smallpox, it has made somewhat of a comeback in the last few years as more and more people decided to not vaccinate their kids against the virus. Ironically these movements are primarily based in the developed world where people have forgotten how much of a serious disease measles still is.
Kids who overcome a measles infection have a higher chance of getting other diseases afterwards because the measles virus kills Memory Cells.
being infected with measles erases the capacity of the immune system to protect you from the diseases that you overcame in the past. Even worse, a measles infection can wipe away the protection that you might have gained from other vaccines, since most vaccines create memory cells.
a toxic substance is nothing more than a molecule that disrupts natural processes or causes damage by destroying or dissolving structures. Antibodies can neutralize these molecules by binding to them with their pincers and rendering them harmless.
the bites of venomous animals are so dangerous because the damage their toxins cause is pretty much instant and only gets worse.
Passive immunization also occurs naturally during pregnancy, when certain antibodies can pass through the placenta and enter a fetus to give it the protection of its mother. What is even more interesting is that once a baby is born, large quantities of antibodies are passed on via human breast milk.
Antibodies are collected from donated blood at blood banks, pooled together, and carefully infused into patients that suffer from immune disorders and are unable to produce Antibodies themselves.
If you administer Antibodies to someone, they will stay protected as long as the Antibodies are around. But this protective effect goes away as the Antibodies are either used up or decay through natural processes.
the principle of live-attenuated vaccines, where we put the real thing into our bodies, but a weak version of it.
another method is to straight up kill the pathogen before injecting it, which is called an inactivated vaccine.
the dead remains of the pathogens have to be mixed with chemicals that highly activate the immune system.
In the case of the hepatitis B vaccine, parts of the virus DNA are implanted into a yeast cell. The yeast cell then produces massive amounts of virus antigen that they display on their outside where it can be harvested.
Just like other inactivated vaccines, the antigens need to be mixed with insulting chemicals that make your immune system think they are dangerous.
And lastly, let us mention the newest type of vaccine, the mRNA vaccines.
The Human Immunodeficiency Virus, or HIV, is a really terrifying but fascinating example to showcase what happens when your immune system breaks down.
all the horror of HIV and AIDS is because it knocks your Helper T Cells out.
HIV enters your cells via specific receptors called “CD4” that are found on the surfaces of Helper T Cells
HIV is a retrovirus which means that it intrudes and merges with your genetic code,
The human genome project found the genetic remains, living fossils, of thousands of viruses in our DNA, comprising up to 8% of our genetic code.
Think about what HIV really does by specifically attacking T Cells: It destroys and kills the cells that the Adaptive Immune System needs to properly activate B Cells and Killer T Cells.
Not only are your Helper T Cells constantly being infected by HIV, Killer T Cells viciously hunt them down too. (That is because, if your Helper T Cells show HIV antigens in their display windows, Killer T Cells will order them to kill themselves!)
As the years pass, the total amount of Helper T Cells is slowly getting lower and lower and lower. Until one day a critical threshold is reached and the Adaptive Immune System collapses.
HIV infections used to be a death sentence, with the disease marching towards an eventual outbreak of AIDS that was soon followed by death.
Almost all therapies for HIV are targeted at preventing the last stage—to prevent AIDS from ever breaking out, because this is where people die.
When your immune system loses its self-composure, it becomes deadly, killing a few thousand people by anaphylactic shock each day.
The most common immediate hypersensitivity reactions in the developed world are hay fever, asthma,
short piece of protein, say from crabmeat, that can be recognized by your adaptive immune cells and antibodies and that causes allergy is an allergen.
IgE is produced by specialized B Cells that tend not to be stationed in your lymph nodes, but in your skin, lungs, and intestines:
The allergen floods your system and for some reason, B Cells that are able to bind to them with their receptors are activated. They begin making IgE Antibodies against the allergen,
IgE Antibodies by themselves would not be problematic as they are not particularly long-lived and dissolve after a few days.
Mast Cells are large, bloated monsters filled with tiny bombs that carry extremely potent chemicals like histamine that cause rapid and massive inflammation.
Mast Cells serve as inflammation superchargers.
Mast Cells have receptors that connect and attach to the butt regions of IgE Antibodies. So if IgE is produced after your first exposure to an allergen, Mast Cells swoop them up like a large magnet would swoop up a bunch of nails.
IgE on Mast Cells is stable for weeks or even months—the connection protects them from decay.
Your armed Mast Cells undergo degranulation, which is a nice way of saying that they vomit out all of their chemicals that are inflammatory superchargers, especially histamine.
It tells the blood vessels to contract and let fluid stream into the tissue, causing redness,
histamine can cause the smooth muscles in your lung to contract and make breathing hard or even impossible.
As there are a lot of Mast Cells in the lungs, allergic reactions that happen here can become dangerous very quickly, as extra fluid and mucus fill up the lung, while it becomes harder and harder to actually breathe. The worst case can be an anaphylactic shock, which can kill within a few minutes.
