|MadSci Network: Medicine|
Hi Ann, I just spotted your question awaiting an answer. Sorry it took so long. First, your physician can order a blood type done on your husband, but he might have to pay a fee. Alternatively, if he donates blood at a local hospital or the Red Cross, he can check back with the blood bank's medical director or other appropriate staff within a couple of days of his donation and they can tell him, since all donor blood has to get typed before use. That way he gets the information for free and he also does a public service! As to your daughter's jaundice, here's how it works. The difference between type A, B and O blood is whether there is a particular type of sugar molecule on the end of a sort of molecular chain on the surface of your red blood cells. This trait is determined by a gene you inherit from your parents. If it's one kind of sugar, you're type A. If it's another kind, you're type B. If you don't have either one, you're type O, and if you have some of both kinds, you're type AB. It so happens that these same sugar molecules are found in food, dust, and a lot of other places, and your body becomes immune to the ones you don't have as part of your own self. So your immune system makes lots of antibodies against these molecules (things that elicit an antibody response are called "antigens"). Antibodies bind to foreign substances in your body and help eliminate them. So if you're type A, you make anti-B because the B antigen is not a normal part of your body. If you're type B, you make anti-A. If you're type O ("universal donor"), you don't have either A or B antigen in your own body, so you make anti-A and anti-B, and if you're type AB ("universal recipient"), you don't make either one. The + and - refer to a different system of blood group molecules, the Rh system, which is involved in some very serious cases of newborn jaundice, but that's another whole story. Now, antibodies to A and B are mainly made up of a class of antibody molecules called IgM. IgM antibodies cannot cross the barrier of the placenta between the mother's and baby's circulation. But some antibodies are of the IgG class, and these do cross the placenta. This protects the baby from everything the mother is immune to, and it gives newborns a kind of 6-month warranty during which the antibodies they got from Mom protect them from many infections and diseases. Once the antibody levels drop down, then the kids are on their own, and seem like they catch every cold that comes through town. It so happens that the levels of IgG antibody against A or B antigen can be fairly high in type O people. That antibody can cross the placenta and kill red blood cells in the baby's circulation, and the orange pigment called bilirubin builds up in the baby's circulation as a result. Bilirubin is toxic to the nervous system at high levels. Before birth, the mother's liver handles this with no trouble, but the baby's liver is small and can't handle the load after birth, and this leads to jaundice - usually mild and easily handled by ultraviolet light, which de-toxifies the bilirubin. If the problem is more severe, a transfusion can manage it. You being type O and your daughter type A would be a classic case of neonatal jaundice due to ABO incompatibility. I hope this answers your question. Paul R. Odgren, Ph.D. Cell Biology University of Massachusetts Medical School Wocester
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