|MadSci Network: Cell Biology|
Your question is a little vague, but I will answer it in a general way. Humans can't have transfusions of animal blood, because our immune system will recognize it as foreign and mount an immune response. This type of systemic immune response will cause the body to go into shock and probably die. During development, the cells of the immune system are tested in the thymus to make sure they do not attack "self" proteins (called self antigens). Even an animal that is very similar to a human, such as a monkey, has enough differences in their proteins that our immune system can recognize it as different and foreign. This is caused by very slight differences in the protein sequences. Different sugars on the cell surfaces can also be recognized by the immune system. Our immune system is very good. That is why even two humans must be carefully matched to donate and receive blood. If you got blood from someone of a different incompatible blood type, your immune system would attack it. For example, if you have type O blood, you can only receive type O blood. You can not take type A or B blood, because that blood has different sugars on proteins on the blood cells which your immune system will recognize and attack. Erin Cram, Admin MadSci Network
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