Blood

There are four different blood types, A, B, AB, and O. Type A has A antigens, that are lollslipop shaped antigens all over it. These antigens produce B antibodies. Type B's antigens are cone shaped and produce A antibodies. Blood type AB has both shaped antigens, and does not produce any antibodies. Type O blood does not have any antigens and produces both A and B antibodies. The RH factor has a spring shaped figures on them and can be traced back to the Rhesus Monkey. A RH factor is an antigen.
If a women has a negative RH factor and she has a kid that has a positive RH factor or has a blood transfusion that has a postitive RH factor, then the mother's body will build up antibodies against the positive RH factor. The women must have a shot within the first ten days of being exposed the the postive RH factor blood. If she does not get a shot within the first ten days then she will build up antibodies against the positive RH factor that she will never get rid of. If she does not get the shot and decides to have another kid, if the kid has a positive RH factor, then the mother's antibodies will attack the baby's hemoglobin and suffocate the baby causing a miscarriage or a mental disability.