Originally posted by: itachi_
that - and + dosen't really matter it's something with the birth, if mother and father has + then you'll get + and so on, dosen't really matter.. and if you're having a child if you're one - and one + then it could be complicated, something like that.
The - and + actually does matter, - can donate to both + or -, but + can only donate to +. There are in fact not only 4 blood types(AB, B, A, O), but 8, because each - or + counts as a seperate one. That also means O negative is the only blood type that can donate to anyone, and AB+ can only donate to AB+.

Back to topic, I have no idea what my bloodtype is.