The process of apheresis involves removal of whole blood from a patient or donor. Within an instrument that is essentially designed as a centrifuge, the components of whole blood are separated. One of the separated portions is then withdrawn and the remaining components are retransfused into the patient or donor.
The components which are separated and withdrawn include:
The purpose of therapeutic apheresis is to remove a component of the blood which contributes to a disease state. Examples include:
Within the plasma are contained antibodies and antigen-antibody complexes that may contribute to the deleterious effects of autoimmune diseases. Removal of the plasma (and replacement with saline solution) will help to reduce circulating antibodies and immune complexes. In rare circumstances, excess blood proteins are present that may cause circulatory problems. Examples of these diseases include:
Rarely, in myeloproliferative disorders, the platelet count can be very high (thrombocytosis). Removal of platelets can help to avoid complications of thrombosis and bleeding.
In some cases of leukemia with very high white blood cell counts, removal of the excess leukocytes may help to prevent complications of thrombosis.
Stem Cell Harvesting
The small number of circulating bone marrow stem cells can be harvested to use in hematopoietic stem cell transplantation procedures.
Simple phlebotomy can be performed to remove excess substances in the blood in addition to obtaining samples for laboratory testing. For example, the patient with hereditary hemochromatosis must undergo regularly scheduled blood draws to remove excess iron stores.