Hemolytic Disease of the Fetal Fetus and Newborn With Red Cells

There are 35 different platelet allyl antigens that have been discovered to date. HPA1, HPA2, HPA3, HPA4, HPA5 each have a high frequency and low frequency allele. If you're homozygous for one or the other of those, then you can make antibodies against it. And so when they conceive a child and that 1A antigen gets passed on to the fetus, then during pregnancy, if mother gets exposed to that antigen in some way, typically we would think that it's platelets from the baby,. They get into maternal blood and she gets immunized. Then she can make antibodies which cross the placenta during