What's your blood type?

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My mother is B-, My father is A+. Both my twin brother and I are A+... Same phenotype ! That makes us AO+.
I love genetics !

O-

My blood can (theoretically) be placed in anyone. However, I can only receive O- blood.

Story time:

The ABO system.
There are three possible genes, A, B, and neither. If you have neither gene, you are group O. If you have at least one of the A gene and none of the B, you are group A. If you have at least one of the B gene and none of the A, you are group B. If you have one each of A and B, you are group AB. People make naturally occuring antibodies to the A's and B's that they don't have... AB people make no antibodies, and can thus receive blood of any ABO type, A's make anti-B, B's make anti-A, and O's make anti-A and anti-B. We're not quite sure what causes this, one theory I've heard is that intestinal bacteria have antigens similar to A and B, and we're exposed to them early in life, causing immunisation.

Group O red cells can be transfused to anyone, because they have neither A or B antigens on them - but group O plasma is full of anti-A and anti-B, so it can only be given to Os. The reverse applies to A - in fact AB cells can actually kill an O recipient by a type of allergic reaction, but AB plasma is harmless for everyone.

The person who said that her mother is O and her sister is AB... well, something's not right there. Either your sister is actually your half sister and had a different mother, or you've got the groups wrong. It is possible that your mother has what we Blood Bankers call a weak subgroup of either A or B (weak subgroups of A are much more common than of B) and thus looks like group O even though she's actually something else... but if that were the case, the sister should test the same way.

The Rh(D) system:
There is only one gene, and you either have it or you don't. If you have at least one copy, you're Rh(D) positive. If you don't, you're Rh(D) negative. If you are a pregnant D- woman, and your baby is D+, and there's a trans-placental bleed (which can happen spontaneously, or due to amnioscentesis or other procedures), then there's a chance you'll make antibodies to the D antigen present on your baby's red blood cells. For this reason, whenever Rh(D) negative women have the kind of procedure that can cause such a bleed, they get given a blood product called Rh(D) immunoglobulin - it's a slightly modified form of the antibody that your immune system would make, but because it does the work for you, your own immune system never has a chance to get immunised. If the bleed goes undetected, and the woman makes anti-D, then it can cause problems for the baby, including in the worst cases, death. It will also be a problem for any subsequent pregnancies, if the next baby is D+. The bit about it only causing problems for the second birth is because the most common immunising event is childbirth itself, so usually the first baby is clear before the mother makes anti-D.

The rest of the Rh system:
There are also genes called C, c, E, and e, which code for other antigens. These antigens are less likely to cause immunisation than D, but it still happens. And there's no immunoglobulin for them, unlike for D, probably because it's just not that big a problem.

The Kell system:
There are a bunch of genes in this one, the most important of which are called K and k. 92%, or thereabouts, of the population are K- k+, and can form anti-K if exposed to it. Less than 1% are k-, so we Blood Bankers are terrified of them - if they make anti-k we're kinda screwed when it comes to finding blood for them.

Other systems:
There are heaps of them, and they mostly come in pairs - e.g. Duffy A and Duffy B, Kidd A and Kidd B, etc. If you are exposed to an antigen that you don't have, you might make an antibody to it. It will usually not be a problem until the next time you are exposed to it, for this reason we have to do tests on people every 3 days if they've had blood recently and want more. But occasionally people have what we call a delayed-transfusion reaction, because they had a unit from a donor with a different set of antigens, and they've made antibodies to it over several days, and then start to react to it.

More than you ever wanted to know, I'm sure, but this is my job, so trust me, it's all accurate.

I'm A2B (A2 is one of those above mentioned weak subgroups of A, if given regular AB blood there's a slim chance I'd make what we call anti-A1, an antibody that usually only reacts at room temperature and is thus not considered clinically significant).

I'm C+ c+ D+ E- e+ so (if given E+ blood I could make anti-E, which does react at internal body temperature, and thus would make me a slightly difficult crossmatch - fortunately E- blood is not hard to find).

I'm K+ k+ (which means I can't make either antibody, but if I have a K+ baby with a K- woman it's quite likely she'd make anti-K, which can cause serious problems).

I've got a few other typings (one of the first things we do as students is type ourselves for every damn thing), but this is getting beyond a joke, so I'll leave it at that

_________________
Diagnosed but unconvinced... I reckon I'm just a rude and arrogant wierdo

O+

(I hope no stalkers see this)

A+