When a person gets an organ transplant the body’s immune system will reject and attack the organ because of foreign DNA. Why does this not apply to blood transfusions?
In: Biology
It *does* apply to blood transfusions. That’s why you need to match the blood type. The blood type (A, B, AB, 0 etc.) refers to different kinds of proteins on the surface of the blood cells. If your body detects blood cells of the wrong type, it will attack and destroy them.
Blood type 0 does not have any of these proteins on the surface, so people of this type are “universal donors”, i.e. their blood can be safely given to all other people regardless of blood type.
Conversely, people with blood type AB are “universal recipients”. Because their own blood as both type A and type B proteins, their immune system won’t attack blood of any type.
(Note that this isn’t the full story, there are other blood type systems in addition to the AB system.)
Bonus info: With organ transfusions, one issue is that the recipient’s immune system rejects the organ. But it sometimes happens that the immune cells from the donor that are still in the donated organ start attacking the recipients whole body (graft-vs-host disease)! This doesn’t happen with blood transfusions because they typically filter out the white blood cells (immune cells) and only transfer the red blood cells and/or plasma.
It’s not DNA that’s causing the problem (at least not directly), and you do have to worry about it with blood transfusions which is why blood has different types (A, AB, O-, etc.)
Red blood cells don’t have nuclei and therefore don’t have any DNA and generally DNA isn’t what your immune system targets. It targets foreign proteins… which, yes, would have came from translating RNA that may, or maybe not have been transcribed from DNA.
All human cells have little markers on their surface made out of protein. Our white blood cells eat any cells that don’t have the correct markers. It applies to both blood transfusion and organs. Little antibodies attach to the markers that aren’t ours and cause the blood to coagulate by sticking to one another (the antibodies).
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