The October 15, 2000 WT has an article which states, "Nevertheless, Jehovah’s Witnesses respect the principles God included in it, and they are determined to ‘abstain from blood.’ 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."
It doesn't mention DFing and I don't know if anything has changed now that fractions are acceptable.