Apheresis blood donation is a process where whole blood is removed from one arm, centrifuged - removing particular components such as plasma, platelets and white blood cells, and then the remaining blood is returned to the donor usually through the other arm. A continuous circuit.
The Society's current stance on autologous and allogenic blood donation is this:
w00 10/15 p. 31 Questions From Readers ******
Hence, we do not donate blood, nor do we store for transfusion our blood that should be ‘poured out.’ That practice conflicts with God’s law.
In the same article, it states further:
w00 10/15 p. 31 Questions From Readers ******
For example, during certain surgical procedures, some blood may be diverted from the body in a process called hemodilution. The blood remaining in the patient is diluted. Later, his blood in the external circuit is directed back into him, thus bringing his blood count closer to normal. Similarly, blood that flows into a wound may be captured and filtered so that the red cells can be returned to the patient; this is called cell salvage. In a different process, blood may be directed to a machine that temporarily carries on a function normally handled by body organs (for example, the heart, lungs, or kidneys). The blood from the machine is then returned to the patient. In other procedures, blood is diverted to a separator (centrifuge) so that damaging or defective portions of it can be eliminated. Or the goal may be to isolate some of a blood component and apply that elsewhere on the body. There are also tests in which a quantity of blood is withdrawn in order to tag it or to mix it with medicine, whereupon it is put back into the patient.
From this article we can establish a few facts. First, the Society prohibits whole blood donations. Granted, the article does not specifically mention whole blood, but taken in context, that is what it is referring to. Secondly, it is acceptable for a witness to allow hemodilution which is the process of blood leaving the body and returning to it in a continuous circuit. Did you notice closely where the above paragraph said, "blood that flows into a wound may be captured and filtered so that the red cells can be returned to the patient?" Is there a reason for mentioning red cells and not just blood? And thirdly, it is also acceptable for a witness to allow their blood to be centrifuged down to a component which can be injected or applied "elsewhere on the body." The only way to apply a particular blood component elsewhere on the body is through injection. To be able to accomplish this, the blood component must be removed from the body while not being part of the continuous circuit anymore.
The question remains, is it acceptable for witnesses to donate blood components through the process of apheresis? According to the reasoning of the Watchtower article shown above, it is. Why? We have already established that a witness can have his blood leave his body and then return back through a continuous circuit. Apheresis donation is almost identical in this process. Whole blood leaves your body and then returns, minus a component or two, in a continuous circuit. Apheresis donation extracts through centrifuge a component of your whole blood for use in a transfusion to another patient. The Society says that you can isolate a blood component via centrifuge and use it elsewhere on your body, outside of the continuous circuit. This blood component does not need to be discarded or 'poured out.' The Society even further expands on this by saying that you may have your blood withdrawn, "tag it or mix it with medicine," and then retransfuse it back into yourself.
So can a witness donate through apheresis? According to my conscience and with the help of the Society's medically accurate publications, I should be able to.
Like the Society can tell me what to do anyways...
http://www.redcross.org/services/biomed/blood/learn/apheresis.html
http://www.bloodnj.org/apheresis.htm