Why is a person with O negative blood considered a universal donor, but can only receive O negative blood? How rare is O negative?

malarson

The way blood types work is that there are certain proteins that cover the outside of RBCs (red blood cells). The three types of protein are A, B, and rh. If someone has the A protein, then they are blood type A. Is someone has the B protein, then they are blood type B. If they have both, they have AB. If they don't have any, they have blood type O. The rh factor is a third protein, and if it is present on the RBCs, then that person is positive. Vice versa for negative. If a person has type A, they can't receive either B or AB, because the B protein is foreign to their body, and it will be rejected. The same goes with the rh factor: if someone is negative, then they can't receive positive. O negative is the universal donor because there are absolutely no proteins on the RBCs, which means that anyone can receive that blood without suffering rejection. That is the same reason that people with O negative can only receive O negative. AB positive is considered the universal recipient, because every protein is present on the RBCs. As to how rare O negative is, I don't know. Aug 24 06, 8:00 AM

zbeckabee

Here's a link to Landsteiner's findings: http://sln.fi.edu/biosci/blood/types.html Here's a link to the numbers of people AND donor info: http://chapters.redcross.org/br/northernohio/INFO/bloodtype.html Aug 24 06, 8:25 AM

teash

Thank you! Especially the link; it was just what I was looking for! Aug 24 06, 11:00 AM