Having recently posted about vaccines, I went down a much deeper read about the immune system over the past month. It is incredible how many different ways your immune system works in order to keep you safe. However, it's also the same about the many different ways bacteria and viruses can take over your body.
Your immune system has two parts. It has an innate system and it has an adaptive system. The innate system is always there, protecting you from primary infection. Bacteria that might somehow get through your skin, or perhaps some smoke you breathed in. Macrophages, the garbage trucks of your innate system constantly roam your body, picking up things that shouldn't be there, pulling them inside, and dousing them with chemicals to break them down. Have a tattoo? Your macrophages tried their best to pull in the metallic ink particles and clean your body of the foreign mass. That is why those sharp tattoo lines get fuzzy over time.
Did you happen to inhale some smoke? Those smoke particles get pulled in within your lungs and broken down. Your lungs are very exposed compared to much of your body, so special varieties exist there. So in short, these are very important for your immune system and your body. As other types of immune cells destroy invaders, the body parts from battle get absorbed by these.
What does that have to do with the Measles? Measles is a virus that infects people via airborne water droplets from your breathing. This is the same as the common cold, the flu, and Covid-19. It is considered very infectious, meaning your body produces a lot of the virus when infected, and it takes less of the virus landing in a host's nose, throat, lung mucus in order to cause an infection. There is a vaccine for this, and the vaccine has been administered to the majority of the US population.
The vaccine produces a fake infection of Measles. A broken-down version of the virus's pieces is injected along with other chemicals that produce an immune response in your body. This tells your body that things are going bad right now, and they need to call in the adaptive immune system to solve this. Your body has a dozen or so cells for every type of antigen that could possibly exist. This in itself is insane, but that is a core piece of the immune system.
When you get an infection, be it bacterial or viral, the macrophages and neutrophil cells are the primary means of attack. Macrophages are pulling things in and destroying them. Neutrophils are either grabbing onto the attackers to do the same or expelling their toxic insides to simply destroy everything and anything around them. If you've ever had a bad toothache, chances are that the neutrophils are trying to destroy the infection along with your bone, leading to intense pain.
If the infection can't be beaten, the adaptive immune system requires information so that it can create a proper response to your infection. Dendritic cells come to the site of the infection and start to pick up pieces of the invader. The next step is to take these pieces to your lymph nodes, through your lymphatic system.
When your body takes the pieces back to your lymph nodes, it is trying to find the matching immune cell for this infection. Once it does, the cell starts to multiply quickly and is off to fight the infection. These are the T and B cells that are spoken about so often. There are many varieties of these, and sub-varieties, and specialty cells, but in short, your body has figured out the cure and is sending an army.
These usually do the trick. For example, B cells create antibodies, which completely cover up any free-floating viruses. The T cells will tell infected cells that they are compromised and that they need to kill themselves in a way that also wraps up any virus particles within.
When a virus first takes hold, it has the advantage. It can reproduce and hide faster than your body can handle it. It's this adaptive response that helps win the war. When the war is won, many of the cells turn into memory cells and constantly produce antibodies and attack cells that may become infected with the virus.
However, Measles isn't just a common virus. It infects macrophages and several other types of immune system cells. Once you are cured of a virus, it's those memory cells that grant you what is known as immunity. But, Measles infects and kills those cells. If you get a severe enough infection of the Measles, years and years of immunity can be wiped by one infection. All of those colds that you had and beat, are now back on the table. And depending on the infection, you might never be able to self-cure that infection again. Your body only produces about a dozen of each type of response cell combination, so if Measles kills them, you get the picture.
So, people invented vaccines. This creates the memory cell army for a known pathogen early so that you can be ready for an attack. As more and more people get a vaccine, the fewer people the virus can infect and the fewer people that will transmit the virus to others. Your immune system can handle a great number of challenges, but here is a simple analogy that may help.
Imagine yourself at home one night, and someone attacks your house. They arrive by surprise and were able to knock down your door. So a countermeasure against an invader may be having a gun or other weapon in the house. If you have 0 weapons in the house, you have less of a chance of surviving the attack. If you have weapons everywhere, you have a great chance of getting rid of the attacker. Getting a vaccine is quite the same as going out and buying guns. You have anticipated an invader and you are ready.
The whole process of your adaptive immune system finding the right immune cells takes days. It's sort of the same as you being run out of your house and coming back with an army. In the meantime, your house gets looted, or worse, burned down. Had you been vaccinated (had the weapons), the attacker wouldn't get a chance to even get through the front door. Most of the time, your house might be ok. You get looted, it takes time to replace the lost furniture. But sometimes, the looters are very organized and your house is gone.