Just recently got a flu shot, and it got me wondering: who or what exactly is our immune system?
I understand the basic concept of vaccines (i.e. injecting with a weaker version of the pathogen or mRNA so that our bodies are able to produce the necessary proteins to destroy the intrusive body quicker next time). Correct me if this is wrong.
The thing is, who exactly stores this information? Who in our body detects the virus, and tells the body to produce X or Y thing? How does it know this was seen before? How come they are able to store this information for every foreign body that has ever entered our organism?
The whole analogy of white blood cells being like “cops” and vaccines acting as those “wanted” posters make sense, but I imagine this works differently in our body.
Thanks
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What do you mean “who”? Would you ask who is our digestive system?
According to the anime titled “cells at work” theres a network of cells that stores those information so they could deploy what antibodies needed
[certain cells](https://en.m.wikipedia.org/wiki/Immunological_memory) are responsible for that stuff. They basically remember how to kill a previous antigen and when it’s encountered again they go through their notes and remember how they did it last time and spread the word and start making the correct defenders to kill it again.
Edit: I’ll have to search for the video but basically your immune system is capable of killing any antigen it gets infected with. It’s a race though: is your body fast enough to find the correct thing to “kill” the enemy before it overwhelms your cells and kills you.
B cells. B cells roam around and are all like “bitch, whatchu doing here?” (they start every sentence with “bitch…”, that’s why they’re B cells) If they don’t like the answer you give they straight up cut you and take a piece of you to take to their dog, Antibody. Antibody gets that scent of you, boy, and now you fucked. B cell tells Antibody, “bitch, seek” and seek he does, cuz he’s got your scent. B cell got these other boys on the street, Macrophages, that look out for Antibody when he’s seekn’ and when Antibody starts barkin, Macrophage come to finish the job. So don’t get cut in them streets.
(I took immunology 5 years ago, I don’t use it for work, and this is what I pieced together just now. Way more complicated but this is the gist of adaptive immunity)
*u/Jkei is the real deal. Thanks for your knowledge. Don’t get cut in them streets.
/u/NoYoureTheAlien puts forth a neat analogy about B cells, but even as an active B cell immunologist I had to read that twice. It also misses most of the stuff that leads up to a proper B cell response and left out the other main end product of adaptive immunity, namely T cells.
So, let’s take it from the top.
Pathogen gets inside you. Some of them die to elements of *innate* immunity, those parts of the immune system that are more general-purpose and always there. These include a bunch of cells from neutrophils to macrophages and NK cells, as well as the complement system of proteins.
Dead pathogen gets picked up by certain scavenging cells, and while that *can* include B cell or macrophages, by far the most important of these is the dendritic cell. These are best equipped to acquire antigens (catching and cutting up live pathogens themselves, too), travel to the nearest lymph node and start presenting that antigen to any naive T cell it comes across.
Most of these T cell interactions will lead to nothing, until eventually one of them registers a match with its specific T cell receptor, and it enters into a much closer interaction with the dendritic cell. Like going from handshakes to hugs, if you will. They exchange signals that will not only tell the T cell to rapidly multiply, but also adopt one of several programmes of changes that will make it optimally suited to fight the class of pathogen that the dendritic cell ran into. After all, it takes a different approach to kill a fungus than it takes to kill a virus, or a multicellular parasite.
So these T cells multiply, and take action depending on their new programming. Once there’s a bunch of them, they’ll leave the lymph node and start producing signals that similarly put other cells into a suitable defense programme wherever they go. We call these helper T cells. They can also help cytotoxic or “killer” T cells to get in gear (dendritic cells can do that directly, too). These killer T cells are specialized towards killing cells of the own host body when those display distress signals or signs of infection, and they’re most useful against viruses and similar bugs that hide inside your cells.
At the same time, still in the lymph node, you some helper T cells stick around and move over to the B cell follicles. B cells have very specific receptors just like T cells do; it’s the antibody they can later produce, but still stuck in their membrane. So, when some antigen floats into the lymph node, some of these B cells will catch it and start trying to present it to any T cells willing to listen. If you already had a helper T cell response gearing up, those will fulfill that role, and kick off the so called germinal center reaction. The GC reaction is like evolution of a miniature scale; every round, B cells will mutate their antibody to try and make it bind a little better, and compete with each other over the available T cell help. Only the ones that generate the best antibodies will be given signals to survive and multiply. Eventually you end up with a few very optimized B cell “families”, and they’ll go on to produce a ton of antibodies to dump into the blood and spread everywhere.
Lastly, what about immune memory? When you get a response like this, you mobilize huge armies of very specific cells, but after the threat is over they’re no good against anything else, and that’s a lot of mouths to feed for no gain. So, they die off — but some don’t. Whether the cells that go on to survive as memory B and T cells are surviving effector cells or made a decision from the start to become dedicated memory cells is still a bit uncertain. But survive they do, and next time they spot their specific antigen, they can kick off a fresh immune response much, much faster because they’re no longer (as) dependent on dendritic cell help.
Hope this helps. I can strongly recommend Kurtzgesagt’s youtube series on immunity if you want to know more. I think it was mentioned in this thread already, but the anime Cells At Work is also hilariously accurate.
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