Why does our body reject other people’s donated organs and require immunosuppressants to be taken but getting someone else’s blood is ok?
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All cells have antigens on them, basically little flags that tell who those cells belong to. If your body sees a cell with flags from a different body, it recons it’s being attacked by something potentially dangerous and goes to get rid of it. So to make sure your body doesn’t destroy that organ you need medicines that slow that reaction.
Blood cells, especially red blood cells, are really easy in that matter. They don’t have as much of those flags, with the most important ones being A, B (or none) and rhesus D. So as long as that matches it’s no problem
A little addition because I know this lol, there are some more antigens but they aren’t as important especially the first blood donation. If you have had multiple blood donations it becomes a bit more tricky. The other antigens are ones you don’t have naturel antibodies against (unlike A, B and D). So the first time is no danger, as your body doesn’t know of its existence until than. The second time your body sees this though it will have antibodies and will still attack this blood. So there is a bit more to blood donation but it isn’t as important ad the AB0 system so you don’t really learn about it unless it’s your field of work.
Than there’s also the fact that blood really doesn’t survive that long, not even half a year. Your organs are supposed to last all life long.
I’m sorry if I didn’t explain this right, as English ain’t my first language. But this is what I was taught now I’m studying to become a clinical lab worker so this is gonna be my whole job lmao. I hope this helps!!
I’ll get a little more specific than the other answers,, but still keep it ELI5 level.
Your body is composed of cells. Cells are little things with walls on the outside, and various things on the inside that lets them do what they need to do.
One part of the inside of most cells is the nucleus. This is where all of the instructions to make or run the cell exists.
Your body has an immune system. This is a system that attacks foreign things that get into the body that might make you sick.
But the immune system shouldn’t attack your own cells, so how does it tell the difference?
In a cell with a nucleus the cell is constantly making new things on the inside that help run the cell and the body. To make sure that the stuff on the inside is recognized as good, the cell has a little special machine or gate on the wall that grabs stuff from the inside, and shows it to the immune system on the outside. If the immune system doesn’t recognize the stuff on the inside, or if the gate itself has a funny shape, the immune system will attack and kill the cell – it’s an invader, or it’s broken in some way.
These gates have many different shapes, hundreds of them, but each person only had six shapes, so if you take someone else’s cells and put them in your body, chances are they will not match, and the immune system will kill them.
Red blood cells do not have a nucleus, and thus do not participate in this process. That’s why a blood transfusion is simpler than an organ transplant. The organ transplant has to be matched with at least 4 of the 6 gates (the gates are called _human leukocyte antigens) otherwise , even with medications, the body will attack the transplant.
There are.other ways the body protects against foreign materials, or course, so the blood type has to be correct as well.
Every cell has markers (antigens) on it. Blood cells have very few of these markers on them. Each blood type has a different set of markers. If you have one blood type, then your body’s immune system has attacker cells that can identify the markers on the other blood types but don’t identify the markers of your blood type.
So if you’re A, you have A markers on your blood cells, and your immune system has attacker cells that identify B markers but not A. The donated blood is also very short-lived.
All our cells have these markers. When you get to organs, there are so many different types of cells, and so there are billions of these markers. Our immune system knows the markers on our cells. But they identify the markers on the donated organ as different and attack it. Donated organs are meant to last very long. Up to decades if possible. We don’t want the body to attack a donated organ, so we suppress the body’s immune system.
** This is a very, very, very basic version of an extremely complex topic, but the basic idea is the same **
Unlike other cells in your body, red blood cells do not have a nucleus, and do not have DNA. They do not synthesize RNA and do not engage in synthesis of proteins. They have no ribosomes and no mitochondria (and so no mitochondrial DNA) either.
In other words, a red blood cell from one person is pretty much functionally identical to a red blood cell from another person, provided they are the same blood type. They don’t keep pumping out a lot of the mismatched stuff that an organ would over time, and that your immune system would identify and attack as foreign.
Other blood cells like white blood cells (leukocytes) do have their DNA and do get rejected, but these generally don’t live very long already, and are not the “point” of a blood transfusion to begin with. So their loss is not particularly noticed.
If someone replaces your fridge, you’re going to notice. If someone replaces a plank in your floor with another plank of the same type, you probably won’t notice a thing.
Blood is a lot simpler and has a lot fewer antigens – that is, things that can trigger your immune system to attack. Blood is *relatively* simple, compared to all of the proteins and tissues things found in an organ.
That said, blood still has *some* antigens that your body *will* eventually notice and attack. It doesn’t matter much, though, because blood doesn’t last very long in your own body anyway. Your own red blood cells only live for about 120 days, after which they are broken down and replaced. A blood transfusion is never meant to be a permanent solution, just a temporary fix to prevent your body from dying before it has a chance to produce its own blood.
As long as the blood matches your blood type, it will take a while for your body to reject and attack the blood. In the mean time, your body will be producing its own blood so by the time the donor blood is destroyed you won’t need it.
Compare that to an organ donation where you almost certainly need that organ to continue living and can’t make your own replacement. You can’t let your donor heart get attacked and destroyed because your body isn’t going to spontaneously generate a new one and you’ll die without one.
Someone’s blood has to be matched to your blood type, else body will reject that too like a foreign donated organ.
Your body can reject blood too if it’s not the right type, fatally so. Beyond that the primary difference is the donated blood isn’t in your body long term, the red blood cells last up to 2 weeks and only make up a portion of your blood. Meanwhile the donor organ is meant to last for years so your body has a lot longer to reject it.
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