In apheresis, blood is removed from a person and then returned after substances are removed from it.
Apheresis can be used to:
Obtain healthy blood components from a donor to transfuse to a person with a disorder
Remove harmful substances or excessive numbers of blood cells from the blood of a person with a disorder (termed therapeutic apheresis)
The different components of blood that can be separated include:
Plasma contains antibodies (immunoglobulins) and clotting factors, which are sometimes separated from plasma.
The 2 most common types of apheresis that are used to remove harmful substances from blood are:
Plasma exchange
Cytapheresis
Cytapheresis may have different names, depending on the type of cell that is removed from the blood.
Plateletpheresis: Platelet removal
Leukapheresis: White blood cell removal
When plasma is separated from the blood, the procedure is called plasmapheresis. Plasmapheresis is often done on blood from healthy donors to obtain plasma for donation or to obtain specific substances such as clotting factors.
Red blood cell exchange also involves apheresis.
Plasma exchange
In plasma exchange, the person's blood is removed, and the plasma is separated from the blood cells and platelets. The plasma is discarded and the blood cells and platelets are returned to the person along with a plasma-replacing fluid, such as albumin.
Plasma exchange is used to treat disorders in which the person's plasma contains harmful substances (often antibodies). Such disorders include multiple sclerosis, myasthenia gravis and Guillain-Barré syndrome (neurologic disorders that cause muscle weakness), anti-glomerular basement membrane disease (an autoimmune disorder involving bleeding in the lungs and kidney failure), cryoglobulinemia (a disorder involving formation of abnormal antibodies), and thrombotic thrombocytopenic purpura (a rare clotting disorder). Apheresis can help control some chronic diseases but generally does not cure them. However, thrombotic thrombocytopenic purpura can be cured with plasma exchange.
To be helpful, plasma exchange must be done often enough to remove the undesirable substance faster than the body produces it. However, apheresis is repeated only as often as necessary because the large fluid shifts between blood vessels and tissues that occur as blood is removed and returned may cause complications in people who are already ill. Immunosupression is also often used to reduce production of these undesirable substances.
There are several specialized types of plasma exchange.
In LDL apheresis,low density lipoprotein (LDL) cholesterol is removed from plasma. This procedure may be done in people who have a high level of cholesterol in the blood and do not respond well to other treatments to lower cholesterol.
In extracorporeal photopheresis, a person's blood is circulated through an apheresis device that selectively collects specific white blood cells (lymphocytes or monocytes). These cells are mixed with an agent that can be activated by ultraviolet light. The treated cells are exposed to the light and are then infused back into the person. Treatment enhances the ability of white blood cells to kill other white cells that are causing autoimmune disease. This procedure can be used in the treatment of graft versus host disease, a certain lymphoma affecting the skin, and rejection of a transplanted organ.
In immunoadsorption, abnormal antibodies or antigen-antibody complexes are removed from plasma and passed through a filter containing certain proteins that bind to the target antibody or immune complex, allowing it to be removed from the body. Immunoadsorption is used in the treatment of several autoimmune diseases.
Cytapheresis
In cytapheresis, excess numbers of certain blood cells are removed. Erythrocytapheresis can be used to treat polycythemia (an excess of red blood cells). Leukapheresis, a type of cytapheresis, can be used to treat certain types of leukemia (a type of cancer in which there are excess white blood cells). Plateletpheresis, a type of cytapheresis in which platelets are removed, can be used to treat thrombocythemia (an excess of platelets).
Red blood cell exchange
In red blood cell exchange, diseased or abnormal red blood cells are removed by apheresis and then replaced by donor red blood cells. Red blood cell exchange is used to treat or sometimes prevent serious complications of sickle cell disease, such as stroke and acute chest syndrome.
