From: Stephen E. <spe...@gm...> - 2006-07-25 14:55:37
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On 7/25/06, Ethan Blanton <ebl...@cs...> wrote: > Allan Clark spake unto us the following wisdom: > > > I'm pretty sure he meant O+ and O-, referring to the blood pH or > > > something. But I'm pretty sure the +/- thing is actually relevant for > > > A/B/AB as well ... > > > > +/- is the "Rhesus" factor, a protein, but that differs from the > > Anti-XX above? Dunno. My service tags had RH ("O NEG", FWIW), but my > > Chinese gf has no understanding of RH factor; maybe it's not a > > well-known thing here. > > That's surprising, as barring massive blood loss I'm pretty sure the > +/- is far more important, medically. Something about couples with > mismatched +/- having babies with pretty serious medical issues (some > sort of autoimmune problem, I think?) if medications aren't involved. > In the US they used to require couples to have blood tests before > getting married for that very reason ... No, I don't think so. Hospitals do not ask for RH+ or RH- when there's a blood shortage, only the ABO group (A/B/AB/O). The A subtype has antibodies that will target antigens found in the B subtype, and vice, versa. O have no antigens, so that they can donate to anyone, but can only receive O(because the receiver might have antibodies for both types). AB can receive any type of blood, but can only donate to AB. Those antibodies are formed in the first years of life. They almost always do not cross the placenta and aren't an issue for babies(even though it happens sometimes). In constrast, without previous exposure, usually a RH- person will have no antibodies. The Rhesus factor is an issue for children when the mother is "-", and the child is "+". Even then, the first child generally is born healthy. However, the mother's immune system has added the antigen to it's "database", plus antibodies are now in circulation. The second baby is at a great risk if it's also +. He might or might not die. A third one is screwed. I'm not a doctor, but that's the information I've learned so far. Feel free to correct me. Stephen |