Originally Posted by casebro
Yes. Donating blood cells (and plasma) is a common medical procedure, the blood is drawn in a continuous system, the cells separated from plasma, the relevant cell layer is removed and the rest of the blood put back into patient.
It all sounds scary, but it is not. You would be donating a buffy coat:
The blood is commonly processed after donation, you almost never recieve a donation of full blood. It is usually erithrocytes plus saline, we use plasma for other patients who need fresh frozen plasma, such as hemophiliacs. The reason why your blood would be put back in you is because there are very few leukocytes in blood as compared to other fractions and only a few percent of them would be NK cells.
This is done through apheresis:
Probably not, but ask your doctor all the same.