Plasmapheresis is a process in which the liquid in the blood, or plasma, is separated from the cells. In sick people, plasma can contain antibodies that attack the immune system. A machine removes the affected plasma and replaces it with good plasma, or a plasma substitute.This is also known as plasma exchange.The process is similar to kidney dialysis. Plasmapheresis also can refer to the plasma donation process, where the plasma is removed and cells are returned to the body.Plasmapheresis can be used to treat a variety of autoimmune disorders, including myasthenia gravis, Guillain-Barre syndrome, and Lambert-Eaton. It can also be used to treat multiple sclerosis. machine removes the affected plasma and replaces it with good plasma, or a plasma substitute. This is also known as plasma exchange. The process is similar to kidney dialysis. Plasmapheresis also can refer to the plasma donation process, where the plasma is removed and cells are returned to the body.