On 7/25/06, Ethan Blanton <eblanton@...> 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.