I asked the question from an elder/circuit overseer substitute: Where in the Bible can we find support to accept fractions? He said, "I will get back to you".
In year 2000 Watchtower published the GB's reason for not prohibiting blood "fractions" (such as cryoprecipitate, cryosupernatant, albumin and a long, long list of other blood derivatives) saying, "The Bible does not give details, so a Christian must make his own conscientious decision before God."
So I asked a then CO "Where does the Bible give details about white cells isolated from blood so a Christian knows accepting this from blood is wrong?
He looked at me with a blank stare and replied, "We have the faithful slave to help us understand that issue". I pressed the issue saying "Yes. I understand the slave gives us its conclusion that accepting white cells is wrong, but what biblical text gives any more detail about white cells compared with cryoprecipitate so we know accepting one is definitely wrong whereas accepting the other may not definitely be wrong?"
He recommended I pray about it. I told him I had prayed mightily about it and so far had not gotten an answer. He suggested that perhaps my prayers were being hindered due to my critical perspective...