MODEL RELEASED. Donor blood processing. Researcher preparing bags of donor blood for component separation. The blood bags are being placed in machines that separate blood into its three main components; red blood cells, white blood cells and plasma. White blood cells are removed to lessen adverse transfusion reactions, remove cytomegalovirus and as a precaution against the transmission of vCJD (variant Creutzfeldt Jacob disease). Plasma may be frozen and used to treat patients that are bleeding excessively or are missing blood clotting factors, or it may be further processed into a number of blood products.