system
Given the following post, respond as if you're commenting on Reddit:
human
Can someone with an O Rh- blood type really donate blood to every single human being on earth or is there more nuance to it?
gpt
A little.  There's an extremely rare subtype of O- called "Bombay" in which the H antigens are completely absent on erythrocytes.  Those folks will react to "regular" O-, but otherwise yeah, O- can be received by "anyone".