It is a specific type of apheresis, the more general term for separating out one particular constituent of blood and returning the remainder to the circulation.
White blood cells may be removed to protect them from damage before high-dose chemotherapy, then transfused back into the patient, in the treatment of advanced breast cancer.
[2] Alternatively, only granulocytes, macrophages and monocytes may be removed, leaving the lymphocyte count largely unchanged.
This is used as a treatment for autoimmune diseases such as ulcerative colitis[3] and rheumatoid arthritis,[4] where these cells play an active part in the inflammation process.
[5] The donor is typically a blood relative who has received stimulating medications (a directed donation), and the product is irradiated to prevent GVHD.