Idiots screaming "Racism" at science

With bone marrow it is the opposite- immune cells are mostly made in bone marrow. So if you gifted me all my bone marrow- I’d have the same immune system as you more or less. If your tissue is very different than mine- the white blood cells from your marrow will see ALL (almost all..) my tissue as “foreign” and attack it!

Some tissue etc. are less sensitive to mismatch. It depends on what you’re donating. The aforementioned bone marrow must come from a VERY close donor while other things like blood aren’t as important as long as the “type” is right.

It is! It's relatively inconsequential for ABO or basic blood compatibility, but for HLA it's pretty important. I would post the link in the comments, but I can't, so if you search for HLA ethnic compatibility, the NCBI article sums it up well!

Well lookie there, I learned something today. Thanks bro!

So it’s not totally accurate to use ancestry as a barometer for donation... but it’s reasonably decent as a “first test” and easier for people to know than: “who was your great to the 4th power grandpas cousins and siblings and...” Of your ancestors were in Asia 3,000 years ago, and mostly made kids with others from the area, then you’ll likely be a close match for someone else who has the same family history because the people involved and the micro organisms etc. will be very similar.

Tl:dr- there is great debate with race and genetics, and we are seeing less genetic difference in “races” than one would think- that said, WHERE your ancestors come from is at the very least important in immune response and markers which prevent the body from rejecting tissue it doesn’t recognize as its own. “Ethnicity,” not “race” is a decent “dummy” indicator as to what conditions ancestors faced and thus- what your immune system is like and how compatible your tissue is. You CAN get a donor from anywhere- but the odds they have a similar immune system are slim since their immune system isn’t just environmental- but partially carried over in genes based on their ancestors immune systems. So you and your ancestors life style and place you lived effects donor compatibility. So mostly true- with importance of closeness depending in part on what is being donated.

As an asides but relevant- it’s also true that donors of many backgrounds are needed. As travel became easier and cross cultural relationships more common- we have seen communities go from relative regional genetic isolation to moving around more and marrying those from vastly foreign backgrounds. That means more people have mixed ethnicities and ancestry groups, and also means that there is just more diversity in possible combinations of hereditary immune response. That means greater diversity of available tissues are needed to find compatible donors in many cases.