I know that a large part of organ transplants are if they’ll stick or get rejected, but why do they do that? I imagine if your body wants to live it’ll take what it can get so to outright refuse a new organ seems a little counterproductive unless there’s something inhibiting that.
In: Biology
Your immune system has an incredibly complex role because it has to detect everything in your body and decide if it is dangerous and must be neutralised, or if it’s harmless. Now unfortunately it would be impossible for your immune system to keep a catalog from birth of every single harmful invader and every harmless invader, instead it just keeps a catalog of your cells, because it knows your cells already, it’s made up of some of your cells. How it identifies your cells is proteins that are on the outside of your cells, the immune system cells can read these proteins like braille, and if it says this cell belongs to brief_skill_1487, then the immune system is happy, and if it says anything else, the immune system goes scorched earth because it isn’t capable of telling the difference between another persons kidney, and a giant colony of infectious bacteria.
Now we have some work around a to help prevent rejection. First we don’t just give kidneys out random, we have managed to develop blood tests that can test the proteins on the outside of our cells so we can compare with other peoples cells and find people who have very similar proteins on the outside of their cells (by sheer random luck, this is why finding an unrelated organ donor is a miracle and a long waiting game), and so you take a gamble and hope the immune system reads the braille and thinks it’s close enough to your cells.
Now our second strategy is by giving patients medications that weaken the immune system, like fixing the odds in your favour by making its braille reading hands have pins and needles so it’s hard to read the braille and therefore less likely to attack the new kidney. Unfortunately this also allows pathogens to cause infections easier since the immune system can’t read there proteins properly either, which is why transplant patients are considered immunocompromised
Unfortunately the new kidney doesn’t last forever and sometimes the body rejects it very fast despite it being matched and taking anti rejection meds, and even if it does work at first and works fine for quite a few years, it won’t last forever because to do that you would need to completely shut down the entire immune system, and that would allow the bacteria that live on our skin and in our mouth and in our gut to kill us VERY fast. As such over time the weakened immune system eventually starts detecting the foreign kidney and slowly attacks it until it stops working and the patient needs a new one
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