What are "neocytes"?
There has been quite a lot of talk about transfusing neocytes, so we had better explain what they are, and why people usually don't use them.
We already explained that red blood cells are made in the bone marrow, and that each one lives for about 120 days (4 months). therefore the red cells in blood are all different ages, ranging from 1 to 120 days old. When you receive a blood transfusion, the older cells start to be destroyed right away. That is why you hemoglobin starts to fall again immediately after a transfusion.
It is possible to partly separate younger red cells from older red cells, by special centrifuges or other methods. The younger red cells collected this way are sometimes called "neocytes". Because their average age is less than that of whole blood, they can last longer in the circulation. Some people have tried to use them instead of the usual kind of blood.
In fact, neocyte transfusions do last slightly better than usual transfusions. The interval between transfusions becomes a little longer, rather less blood has to be given every year, and the amount of iron laid down in the body is reduced. So the idea of using neocytes is reasonable. However, people don't use them as a rule, because they give only a very small advantage, and it is so expensive and complicated to prepare them.