MODEL RELEASED. Donor blood filtration. Laboratory technician hanging up bags of donor blood that are connected to filters (lower centre) by tubes. The downward flow of the blood drives the filtration process. The blood is named whole blood, as it has not yet been separated into its components. These blood components vary in size and can be removed by filters of different sizes. A common filtration stage for whole blood is the removal of leucocytes (white blood cells). This can reduce infections or immune system responses in a patient receiving the blood. Further processing produces blood products used to treat blood disorders or to replace blood lost through surgery or an accident.